Electrical apparatus and wireless communication method for communication device with multiple antennas

ABSTRACT

An electronic device, and method, at a first communication apparatus having multiple antennas includes a memory for storing computer instructions; and a processing circuit configured to execute the stored computer instructions to: based on channel states of channels between the multiple antennas of the first communication apparatus and a second communication apparatus, determine channel characteristics of a first channel from the first communication apparatus to a second communication apparatus in an angle domain: based on the determined channel characteristics of the first channel in the angle domain, determine a first set of pilot signals used in the angle domain, the pilot signals in the first set of pilot signals being orthogonal to each other; and transform the first set of pilot signals into a second set of pilot signals for transmission over the multiple antennas of the first communication apparatus.

FIELD OF THE INVENTION

The present disclosure relates to an electronic device and acommunication method, and more particularly, the present disclosurerelates to an electronic device and a communication method in a MassiveMulti-Input Multi-Output (MIMO) antenna system.

BACKGROUND

Recently, as massive MIMO antenna systems can significantly improve thespectrum efficiency and energy efficiency, massive MIMO antenna systemshave been considered as a part of critical 5G technology in the future,and have attracted wide attention from academia and industry.

In the prior art, in order to make full use of diversity gain andmultiplexing gain of a massive MIMO antenna system, a base station (BS)needs to be aware of the channel state of a channel between the basestation and a user equipment (UE). In a Time Division Duplex (TDD)system, the channel state of a downlink channel between a BS and a UEcan be obtained by using channel reciprocity. Therefore, a large numberof documents in the current are focused on TDD massive MIMO antennasystems. However, TDD systems also face problems such as pollution ofpilot signal (also referred to as training sequence, reference sequence,etc), and it is difficult for TDD systems to support high-speed mobilecommunication scenarios. On the other hand, most current cellular mobilecommunication systems operate in the Frequency Division Duplex (FDD)mode, and therefore the FDD mode is bound to be preserved in theevolution to the 5G standard.

DISCLOSURE OF THE INVENTION

The inventor of the present disclosure has found that, in a conventionalmassive MIMO antenna systems, since a traditional channel estimationmethod carries out channel estimation by sending orthogonal pilotsignals (which may also be referred to as training sequences, referencesequences, etc) via different antennas, the number of physical resourceunits required to send the pilot signals increases with the number ofantennas. Therefore, in the case where a UE or BS is provided withmultiple antennas, as the number of antennas increases, the overhead ofchannel estimation increases, thereby greatly limiting the datathroughput rate of the communication system. Currently, there is nofeasible solution to solve this problem.

Therefore, the present application proposes a new technical solutionaddressed to at least one of the above problems.

One aspect of the present disclosure relates to an electronic deviceused for a first communication apparatus having multiple antennas,comprising: a memory for storing computer instructions; and a processingcircuit configured to execute the stored computer instructions to:determine, based on channel states of channels between the multipleantennas of the first communication apparatus and the secondcommunication apparatus, channel characteristics of a first channel fromthe first communication apparatus to a second communication apparatus inthe angle domain; based on the determined channel characteristics of thefirst channel in the angle domain, determine a first set of pilotsignals used in the angle domain, the pilot signals in the first set ofpilot signals being orthogonal to each other; and transform the firstset of pilot signals into a second set of pilot signals for transmissionover the multiple antennas of the first communication apparatus.

One aspect of the present disclosure relates to an electronic deviceused for a second communication apparatus, comprising: a memory forstoring computer instructions; and a processing circuit configured toexecute the stored computer instructions to: perform channel estimationof a first channel from a first communication apparatus having multipleantennas to the second communication apparatus based on a second set ofpilot signals from the first communication apparatus, wherein the secondset of pilot signals is determined by the first communication apparatusby the following processes: determining, based on channel states ofchannels between the multiple antennas of the first communicationapparatus and the second communication apparatus, channelcharacteristics of the first channel from the first communicationapparatus to the second communication apparatus in the angle domain;based on the determined channel characteristics of the first channel inthe angle domain, determining a first set of pilot signals used in theangle domain, the pilot signals in the first set of pilot signals beingorthogonal to each other; and transforming the first set of pilotsignals into the second set of pilot signals for transmission over themultiple antennas of the first communication apparatus.

One aspect of the present disclosure relates to a communication methodfor a first communication apparatus having multiple antennas,comprising: determining, based on channel states of channels between themultiple antennas of the first communication apparatus and the secondcommunication apparatus, channel characteristics of a first channel fromthe first communication apparatus to a second communication apparatus inthe angle domain; based on the determined channel characteristics of thefirst channel in the angle domain, determining a first set of pilotsignals used in the angle domain, the pilot signals in the first set ofpilot signals being orthogonal to each other; and transforming the firstset of pilot signals into a second set of pilot signals for transmissionover the multiple antennas of the first communication apparatus.

One aspect of the present disclosure relates to a communication methodfor a second communication apparatus, comprising: performing channelestimation of a first channel from a first communication apparatushaving multiple antennas to the second communication apparatus based ona second set of pilot signals from the first communication apparatus,wherein the second set of pilot signals is determined by the firstcommunication apparatus by the following processes; determining, basedon channel states of channels between the multiple antennas of the firstcommunication apparatus and the second communication apparatus, channelcharacteristics of the first channel from the first communicationapparatus to the second communication apparatus in the angle domain;based on the determined channel characteristics of the first channel inthe angle domain, determining a first set of pilot signals used in theangle domain, the pilot signals in the first set of pilot signals beingorthogonal to each other; and transforming the first set of pilotsignals into the second set of pilot signals for transmission over themultiple antennas of the first communication apparatus.

One aspect of the present disclosure relates to an electronic deviceused in a multi-antenna wireless communication system, the electronicdevice comprising: a memory for storing computer instructions; and aprocessing circuit configured to execute the stored computerinstructions to: determine a channel angle between a communicationterminal and a base station (BS) according to a channel state of anuplink channel from the communication terminal to the BS; from aplurality of pilot signals, select a part of the plurality of pilotsignals for the channel angle, wherein the BS has multiple antennas, theplurality of pilot signals supporting channel angles covered by themultiple antennas of the BS; and transform the part of pilot signalsinto signals for transmission over the multiple antennas of the BS.

According to some embodiments of the present disclosure, the overhead ofchannel estimation may be reduced.

According to some embodiments of the present disclosure, it is alsopossible to further increase the data throughput rate of thecommunication system while maintaining lower overhead of channelestimation.

Other features and advantages of the present invention will becomeapparent from the following detailed description of exemplaryembodiments of the present disclosure with reference to the accompanyingdrawings.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentdisclosure and, together with the description, serve to explain theprinciples of the present disclosure.

The present disclosure will be more clearly understood from thefollowing detailed description with reference to the accompanyingdrawings, in which:

FIG. 1 is a diagram showing an example of the configuration of anorthogonal pilot system in the prior art.

FIG. 2 is a diagram illustrating an example of allocating transmissionresources for time-domain orthogonal pilot signals in the prior art.

FIG. 3 is a diagram illustrating an example of allocating transmissionresources for frequency-domain orthogonal pilot signals in the priorart.

FIG. 4 is a diagram illustrating an example of allocating transmissionresources for time-frequency two-dimensional orthogonal pilot signals inthe prior art.

FIG. 5 is a diagram illustrating an example of allocating transmissionresources for code orthogonal pilot signals in the prior art.

FIG. 6 is a block diagram illustrating the configuration of anelectronic device used for a first communication apparatus havingmultiple antennas according to an embodiment of the present disclosure.

FIG. 7 is a block diagram illustrating the configuration of anelectronic device used for a second communication apparatus according tothe embodiment of the present disclosure.

FIG. 8 is a flowchart illustrating an example of a signaling interactionprocedure performed between a BS and a UE according to the embodiment ofthe present disclosure.

FIG. 9 is a flowchart illustrating an example of a signaling interactionprocedure performed between a UE and a BS according to the embodiment ofthe present disclosure.

FIG. 10 is a diagram illustrating an example of a process flow ofdetermining channel characteristics of a channel between a BS and a UEin the angle domain according to the embodiment of the presentdisclosure.

FIG. 11 is a diagram showing an example of the configuration of an angledomain orthogonal pilot system according to an embodiment of the presentdisclosure.

FIG. 12 is a diagram showing another example of the configuration of anangle domain orthogonal pilot system according to an embodiment of thepresent disclosure.

FIG. 13A is a diagram illustrating a channel state of an uplink channelof a first UE according to an embodiment of the present disclosure.

FIG. 13B is a diagram illustrating actual channel characteristics of adownlink channel of a first UE in the angle domain according to anembodiment of the present disclosure.

FIG. 14A is a diagram illustrating a channel state of an uplink channelof a second UE according to an embodiment of the present disclosure.

FIG. 14B is a diagram illustrating actual channel characteristics of adownlink channel of a second UE in the angle domain according to anembodiment of the present disclosure.

FIG. 15A is a diagram illustrating a channel state of an uplink channelof a third UE according to an embodiment of the present disclosure.

FIG. 15B is a diagram illustrating actual channel characteristics of adownlink channel of a third UE in the angle domain according to anembodiment of the present disclosure.

FIG. 16 is a diagram illustrating an example of an angle domaincompletely orthogonal pilot signal sequence according to an embodimentof the present disclosure.

FIG. 17 is a diagram illustrating an example of an angle domainpartially orthogonal pilot signal sequence according to an embodiment ofthe present disclosure.

FIG. 18 is a schematic diagram illustrating an example of allocatingtransmission resources for angle domain completely orthogonal pilotsignals according to an embodiment of the present disclosure.

FIG. 19 is a schematic diagram illustrating an example of allocatingtransmission resources for angle domain partially orthogonal pilotsignals according to an embodiment of the present disclosure.

FIG. 20 is a flowchart illustrating a communication method for a firstcommunication apparatus having multiple antennas according to anembodiment of the present disclosure.

FIG. 21 is a flowchart illustrating a communication method for a secondcommunication apparatus according to an embodiment of the presentdisclosure.

FIG. 22 is a block diagram illustrating the configuration of stillanother example of an electronic device according to an embodiment ofthe present disclosure.

FIG. 23 is a flowchart illustrating a communication method for anelectronic device according to an embodiment of the present disclosure.

FIG. 24 is a simulation diagram of one example of the throughput rate ofa cell in a communication system according to an embodiment of thepresent disclosure.

FIG. 25 is a simulation diagram of another example of the throughputrate of a cell in a communication system according to an embodiment ofthe present disclosure.

FIG. 26 is a block diagram illustrating an example of the schematicconfiguration of a smart phone according to an embodiment of the presentdisclosure;

FIG. 27 is a block diagram illustrating an example of the schematicconfiguration of a car navigation device according to an embodiment ofthe present disclosure;

FIG. 28 is a block diagram illustrating a first example of the schematicconfiguration of an eNB according to an embodiment of the presentdisclosure;

FIG. 29 is a block diagram illustrating a second example of theschematic configuration of an eNB according to an embodiment of thepresent disclosure;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Various exemplary embodiments of the present disclosure will now bedescribed in detail with reference to the accompanying drawings. Noticethat, unless otherwise specified, relative arrangement, numericalexpressions and numerical values of components and steps set forth inthese examples do not limit the scope of the invention.

Meanwhile, it should be understood that, for ease of description,dimensions of various parts shown in the drawings are not drawn inactual proportions.

The following description of at least one exemplary embodiment is infact merely illustrative and is in no way intended as a limitation tothe invention, its application or use.

Techniques, methods, and apparatus known to those of ordinary skill inthe relevant art may not be discussed in detail, but where appropriate,these techniques, methods, and apparatuses should be considered as partof the specification.

In all the examples shown and discussed herein, any specific valueshould be construed as merely illustrative and not as a limitation.Thus, other examples of exemplary embodiments may have different values.

Note that, similar reference numerals and letters denote similar termsin the accompanying drawings, and therefore, once an item is defined ina drawing, there is no need for further discussion in the accompanyingdrawings.

1. EXAMPLE OF THE CONFIGURATION OF AN ORTHOGONAL PILOT SYSTEM IN THEPRIOR ART

FIG. 1 is a diagram showing an example of the configuration of anorthogonal pilot system in the prior art.

As shown in FIG. 1, in a wireless communication system of the prior art,a BS is equipped with M antennas (M is an integer and M≥1), each antennais provided with a corresponding antenna port, and a corresponding RFlink is arranged for each antenna port. In addition, the BS is alsoprovided with a pilot allocation module, which allocates orthogonalpilot signals (also referred to as training sequences, referencesequences, etc) for respective antenna ports. Through correspondingantenna ports and antennas, the BS transmits the orthogonal pilotsignals to one or more UEs over a wireless physical channel.

In the pilot allocation module of the prior art, orthogonal modes ofpilot signals may include time domain orthogonal mode, frequency domainorthogonal mode, time-frequency two-dimensional orthogonal mode, codeorthogonal mode, and other modes. For example, in an OrthogonalFrequency Division Multiplexing (OFDM) system of the prior art, theconfigurations of the above-mentioned orthogonal pilot signals may beillustrated as follows.

FIG. 2 is a diagram illustrating an example of allocating transmissionresources for time-domain orthogonal pilot signals in the prior art. Asshown in FIG. 2, it is assumed that the BS is equipped with, forexample, 8 antennas and 8 antenna ports correspondingly. The horizontalaxis in FIG. 2 represents time, the vertical axis represents frequency,and each block represents a physical resource unit at a certain time anda certain frequency. As shown in FIG. 2, in the case of time-domainorthogonal pilot signals, different antenna ports transmit pilot signalsat different times, but these different antenna ports use the samefrequency to transmit these pilot signals. For example, antenna ports 0to 7 may transmit pilot signals using physical resource units R0 to R7at the same frequency F4, but different times T0 to T7, respectively.

FIG. 3 is a diagram illustrating an example of allocating transmissionresources for frequency-domain orthogonal pilot signals in the priorart. As shown in FIG. 3, it is also assumed that the BS is equippedwith, for example, 8 antennas and 8 antenna ports correspondingly. Also,the horizontal axis in FIG. 3 represents time, the vertical axisrepresents frequency, and each block represents a physical resource unitat a certain time and a certain frequency. As shown in FIG. 3, in thecase of frequency domain orthogonal pilot signals, different antennaports transmit pilot signals using different frequencies (i.e.,sub-carriers at different frequencies), but these different antennaports transmit these pilot signals at the same time. For example,antenna ports 0 to 7 may transmit pilot signals using physical resourceunits R0 to R7 at different frequencies F0 to F7, but at the same timeT0, respectively.

FIG. 4 is a diagram illustrating an example of allocating transmissionresources for time-frequency two-dimensional orthogonal pilot signals inthe prior art. As shown in FIG. 4, it is also assumed that the BS isequipped with, for example, 8 antennas and 8 antenna portscorrespondingly. Also, the horizontal axis in FIG. 4 represents time,the vertical axis represents frequency, and each block represents aphysical resource unit at a certain time and a certain frequency. Asshown in FIG. 4, in the case of time-frequency two-dimensionalorthogonal pilot signals, different antenna ports use differenttime-frequency two-dimensional physical resource units to transmit pilotsignals, that is, physical resource units used by different antennaports to transmit the pilot signals are different at least in time orfrequency. For example, antenna port 0 may transmit the pilot signalusing physical resource unit R0 at frequency F7 and time T0, antennaport 1 may transmit the pilot signal using physical resource unit RI atfrequency F6 and time T4 . . . , and antenna port 7 may transmit thepilot signal using the physical resource unit R7 at frequency F0 andtime T4.

FIG. 5 is a diagram illustrating an example of assigning transmissionresources for code orthogonal pilot signals in the prior art; As shownin FIG. 5, it is also assumed that the BS is equipped with, for example,8 antennas and 8 antenna ports correspondingly. Also, the horizontalaxis in FIG. 5 represents time, the vertical axis represents frequency,and each block represents a physical resource unit at a certain time anda certain frequency. As shown in FIG. 5, in the case of code orthogonalpilot signals, different antenna ports transmit pilot signals that areorthogonal to each other. For example, antenna ports 0 to 7 transmitpilot signals S0 to S7 that are orthogonal to each other respectively.

However, in the various forms of orthogonal pilot signals such as timedomain orthogonal pilot signals, frequency domain orthogonal pilotsignals, time-frequency two-dimensional orthogonal pilot signals, andcode orthogonal pilot signals as described above, the number of physicalresource units required to transmit the pilot signals is the same as thenumber of the antennas or antenna ports. For example, when the BS isequipped with 8 antennas, 8 physical resource units are required totransmit the pilot signals no matter which one of time domain orthogonalpilot signals, frequency domain orthogonal pilot signals, time-frequencytwo-dimensional orthogonal pilot signals, and code orthogonal pilotsignals is used. Therefore, as the number of antennas increases, thenumber of physical resource units required to transmit pilot signalsalso increases. Therefore, in the case where multiple antennas areprovided for a UE or a BS, as the number of antennas increases, theoverhead of channel estimation increases, thereby greatly limiting thedata throughput rate of the communication system.

2. SCHEMATIC CONFIGURATION OF AN ELECTRONIC DEVICE ACCORDING TO ANEMBODIMENT OF THE PRESENT DISCLOSURE

FIG. 6 is a block diagram illustrating the configuration of anelectronic device 600 used for a first communication apparatus havingmultiple antennas according to an embodiment of the present disclosure.

The electronic device 600 for the first communication apparatus havingmultiple antennas according to the embodiment of the present disclosuremay include, for example, a processing circuit 620 and a memory 610.

The processing circuit 620 of the electronic device 600 for the firstcommunication apparatus having multiple antennas is configured toprovide various functions for the electronic device 600 that is used forthe first communication apparatus having multiple antennas. For example,in the embodiment of the present disclosure, the processing circuit 620of the electronic device 600 for the first communication apparatushaving multiple antennas may include a channel characteristicdetermining unit 621, a pilot signal determining unit 622, and a pilotsignal transforming unit 623. The channel characteristic determiningunit 621 may be configured to determine, based on channel states ofchannels between multiple antennas of the first communication apparatusand a second communication apparatus, determine channel characteristicsof a first channel from the first communication apparatus to the secondcommunication apparatus in the angle domain. The pilot signaldetermining unit 622 may be configured to determine a first set of pilotsignals used in the angle domain based on the determined channelcharacteristics of the first channel in the angle domain, the pilotsignals in the first set of pilot signals being orthogonal to eachother. The pilot signal transforming unit 623 may be configured totransform the first set of pilot signals into a second set of pilotsignals for transmission over the multiple antennas of the firstcommunication apparatus.

In addition, the electronic device 600 for the first communicationapparatus having multiple antennas may also include, for example,multiple antennas. These multiple antennas may be configured to transmitthe second set of pilot signals.

According to one embodiment of the present disclosure, the firstcommunication apparatus may be a BS and the second communicationapparatus may be a UE. According to another embodiment of the presentdisclosure, the first communication apparatus may be a UE and the secondcommunication apparatus may be a BS. It should be noted that thecommunication system to which the present disclosure is applied is, forexample, an LTE system, and the BS may send, for example, channel stateinformation reference signals (CSI-RS) or the like adopted in the LTEsystem as pilot signals, reference sequences, training sequences, etc.However, the technical solution of the present disclosure is not limitedto the LTE system. In different communication systems, for example, in afuture 5G communication system, the BS may send other pilot signals,reference sequences, training sequences, etc suitable for channelestimation.

The memory 610 may store information generated by the processing circuit620 and programs and data operated by the electronic device 600 used forthe first communication apparatus having multiple antennas. The memory610 may be volatile memory and/or non-volatile memory. For example, thememory 610 may include, but is not limited to, random access memory(RAM), dynamic random access memory (DRAM), static random access memory(SRAM), read-only memory (ROM), and flash memory.

FIG. 7 is a block diagram illustrating the configuration of anelectronic device 700 used for a second communication apparatusaccording to the embodiment of the present disclosure.

The electronic device 700 for the second communication apparatusaccording to the embodiment of the present disclosure may include, forexample, a processing circuit 720 and a memory 710.

The processing circuit 720 of the electronic device 700 used for thesecond communication apparatus is configured to provide variousfunctions for the electronic device 700 that is used for the secondcommunication apparatus. For example, the processing circuit 720 of theelectronic device 700 for the second communication apparatus may includea channel estimation unit 721. The channel estimation unit 721 may beconfigured to perform channel estimation on a first channel from a firstcommunication apparatus having multiple antennas to the secondcommunication apparatus based on a second set of pilot signals from thefirst communication apparatus, wherein the second set of pilot signal isdetermined by the first communication apparatus through the followingprocesses: determining, based on channel states of channels between themultiple antennas of the first communication apparatus and the secondcommunication apparatus, channel characteristics of a first channel fromthe first communication apparatus to the second communication apparatusin the angle domain; based on the determined channel characteristics ofthe first channel in the angle domain, determining a first set of pilotsignals used in the angle domain, the pilot signals in the first set ofpilot signals being orthogonal to each other; and transforming the firstset of pilot signals into the second set of pilot signals fortransmission over the multiple antennas of the first communicationapparatus. In addition, the processing circuit 720 may further include agenerating unit (not shown) configured to generate a feedback reportabout a channel estimation result based on the second set of pilotsignals to provide the channel estimation result to the firstcommunication apparatus.

According to one embodiment of the present disclosure, the firstcommunication apparatus may be a BS and the second communicationapparatus may be a UE. According to another embodiment of the presentdisclosure, the first communication apparatus may be a UE and the secondcommunication apparatus may be a BS. It should be noted that thecommunication system to which the present disclosure is applied is, forexample, an LTE system, and the BS may send, for example, channel stateinformation reference signals (CSI-RS) or the like adopted in the LTEsystem as pilot signals, reference sequences, training sequences, etc.However, the technical solution of the present disclosure is not limitedto the LTE system, and in different communication systems, the BS maytransmit other suitable pilot signals, reference sequences, trainingsequences, etc.

The memory 710 may store information generated by the processing circuit720 and programs and data operated by the electronic device 700 used forthe second communication apparatus. The memory 710 may be volatilememory and/or non-volatile memory. For example, the memory 710 mayinclude, but is not limited to, random access memory (RAM), dynamicrandom access memory (DRAM), static random access memory (SRAM),read-only memory (ROM), and flash memory.

3. PROCESS FLOW ACCORDING TO AN EMBODIMENT OF THE PRESENT DISCLOSURE

FIG. 8 is a flowchart illustrating an example of a signaling interactionprocedure performed between a BS and a UE according to an embodiment ofthe present disclosure.

As shown in FIG. 8, in step 8003, based on channel states of channelsbetween multiple antennas of a first communication apparatus (e.g., aBS) and a second communication apparatus (e.g., a UE), channelcharacteristics of a first channel (e.g., a downlink channel) from thefirst communication apparatus (e.g., a BS) to the second communicationapparatus (e.g., a UE) in the angle domain are determined.

According to one embodiment of the present disclosure, based on symmetryof antenna angles of arrival in a first channel (e.g., a downlinkchannel) and a second channel (e.g., an uplink channel) between thefirst communication apparatus (e.g., a BS) and the second communicationapparatus (e.g., a UE), channel characteristics of the first channel(e.g., the downlink channel) in the angle domain can be determined fromthe channel state of the second channel (e.g., the uplink channel).

The applicant has noted that although the uplink and downlink channelsin the FDD system are no longer reciprocal, according to the channelmodel provided in WINNER II (see IST-4-027756 WINNER II D1.1.2 V1.2WINNER II Channel Models, Part 1, Channel Model, section 5.4.3),small-scale fading parameters (such as, the antenna angle of arrival) ofthe uplink and downlink channels are the same. Specifically, thedownlink channel H^(DL)∈C^(M×1) and the uplink channel H^(UL)∈C^(M×1)may be respectively represented as follows:

$h^{DL} = {\sqrt{\frac{M}{N_{cl}N_{ray}}}{\sum\limits_{i = 1}^{N_{cl}}\; {\sum\limits_{l = 1}^{N_{ray}}\; {\alpha_{i,l}e^{j\; \psi_{i,l}^{DL}}{a^{DL}\left( {\varphi_{i,l},\theta_{i,l}} \right)}}}}}$$h^{UL} = {\sqrt{\frac{M}{N_{cl}N_{ray}}}{\sum\limits_{i = 1}^{N_{cl}}\; {\sum\limits_{l = 1}^{N_{ray}}\; {\alpha_{i,l}e^{j\; \psi_{i,l}^{UL}}{a^{UL}\left( {\varphi_{i,l},\theta_{i,l}} \right)}}}}}$

wherein, M represents the number of antennas provided for the BS, M is anatural number greater than or equal to 1, N_(cl) is the number ofscatterers, N_(ray) is the number of sub-paths included in eachscatterer, and α_(i,1) represents the channel coefficient of eachsub-path, a denotes the antenna response vector of the BS, thesuperscripts UL and DL represent the uplink channel and the downlinkchannel, respectively, and φ and 8 are the antenna angles of arrival inthe horizontal direction and the vertical direction, respectively. Inaddition, ψ_(i,1) ^(DL) and ψ_(i,1) ^(UL) denote random phases of eachsub-path in the uplink channel and the downlink channel, which areindependently and uniformly distributed in [0, 2π].

Further, the form of the antenna response vector depends on the type ofthe antennas provided for the BS. For example, in the case where all theantennas provided for the BS are Uniform Linear Array (ULA) antennas,the antenna response vector can be represented as follows:

${a_{ULA}(\varphi)} = {\frac{1}{\sqrt{M}}\left\lbrack {1,e^{j\frac{2\; \pi \; d}{\lambda}{\sin {(\varphi)}}},\ldots \mspace{14mu},e^{{j{({M - 1})}}\frac{2\; \pi \; d}{\lambda}{\sin {(\varphi)}}}} \right\rbrack}^{T}$

Note that in the above expression, wavelengths λ^(UL) and λ^(DL) may beused for the uplink and downlink channels, respectively.

As another example, in the case where all the antennas provided for theBS are Uniform Planar Array (UPA) antennas, provided that the numbers ofantennas in the horizontal direction and the vertical direction are Wand H, respectively, and W×H=M, M representing the number of antennasprovided for the BS, wherein W, H and M all are natural numbers greaterthan or equal to 1, the antenna response vector may have a form ofKronecker product, and may be expressed as follows:

a _(UPA)(ϕ,θ)=vec(a _(v)(θ)⊗a _(h)(ϕ,θ))

Wherein, a_(v)(θ) and a_(h)(φ,θ) are the antenna response vectors in thevertical and horizontal directions respectively, a_(v)(θ) and a_(h)(φ,θ)can be respectively expressed as:

${a_{v}(\theta)} = {\left\lbrack {1,e^{j\frac{2\; \pi \; d}{\lambda}{\cos {(\theta)}}},\ldots \mspace{14mu},e^{j\frac{2\; \pi \; d}{\lambda}{({H - 1})}{\cos {(\theta)}}}} \right\rbrack^{T} \in {\mathbb{C}}^{H \times 1}}$${a_{h}\left( {\varphi,\theta} \right)} = {\left\lbrack {1,e^{j\frac{2\; \pi \; d}{\lambda}{\sin {(\varphi)}}{\sin {(\theta)}}},\ldots \mspace{14mu},e^{j\frac{2\; \pi \; d}{\lambda}{({W - 1})}{\sin {(\varphi)}}{\sin {(\theta)}}}} \right\rbrack^{T} \in {\mathbb{C}}^{1 \times W}}$

Similarly, in the above expression, wavelengths λ^(UL) and λ^(DL) may beused for the uplink and downlink channels, respectively.

Thus, due to the reciprocity of the antenna angles of arrival of theuplink channel and the downlink channel, channel characteristics of thedownlink channel in the angle domain can be determined from the channelstate of the uplink channel.

Specifically, channel states of channels between the multiple antennasof a first communication apparatus (e.g., a BS) and a secondcommunication apparatus (e.g., a UE) corresponds to channel states ofchannels from the second communication apparatus (e.g., a UE) to themultiple antennas of the first communication apparatus (e.g., a BS). Inaddition, the channel characteristic determining unit 621 in theprocessing circuit 620 of the electronic device 600 used for the firstcommunication apparatus having multiple antennas may be furtherconfigured to: based on channel states of channels from the secondcommunication apparatus (e.g., a UE) to the multiple antennas of thefirst communication apparatus (e.g., a BS), determine channelcharacteristics of a second channel (e.g., an uplink channel) from thesecond communication apparatus (e.g., a UE) to the first communicationapparatus (e.g., a BS) in the angle domain, and determine channelcharacteristics of a first channel (e.g., a downlink channel) in theangle domain based on the channel characteristics of the second channel(e.g., an uplink channel) in the angle domain.

Return back to step 8001 and step 8002 in FIG. 8. Steps 8001 and 8002 inFIG. 8 are optional steps.

In step 8001, uplink pilot signals may be transmitted from the UE to theBS.

In step 8002, the uplink channel may be estimated according to theuplink pilot signals transmitted from the UE to the BS to determinechannel state of the uplink channel.

Once the channel states of channels between the multiple antennas of thefirst communication apparatus (e.g., a BS) and the second communicationapparatus (e.g., a UE) is obtained, a transformation may be performed onthe channel states of channels between the multiple antennas of thefirst communication apparatus (e.g., a BS) and the second communicationapparatus (e.g., a UE) to obtain channel characteristics ofcorresponding channels in the angle domain. For example, once thechannel state of the uplink channel from the UE to the BS is obtained,the channel state of the uplink channel from the UE to the BS may betransformed to obtain channel characteristics of the uplink channel fromthe UE to the BS in the angle domain.

According to an embodiment of the present disclosure, N angles at whichthe channel characteristics are significant are selected from the angledomain based on channel characteristics of corresponding channels in theangle domain, where N is a natural number greater than or equal to 1,the number of pilot signals in the first set of pilot signals is greaterthan or equal to N, and the first set of pilot signals are used for theN angles, respectively.

For example, based on the channel characteristics of the uplink channelfrom the UE to the BS in the angle domain, N angles at which the channelcharacteristics are significant can be selected from the angle domain,where N is a natural number greater than or equal to 1. According to anembodiment of the present disclosure, the number of the first set ofpilot signals may be greater than or equal to N, and the first set ofpilot signals are used for the N angles, respectively. For example, inthe case of a communication system having only one UE, the number ofpilot signals in the first set of pilot signals may be equal to N. Foranother example, in the case of a communication system having two ormore UEs, the number of pilot signals in the first set of pilot signalsmay be greater than N.

Specifically, according to the embodiment of the present disclosure, itcan be determined whether the channel characteristics of a correspondingchannel in the angle domain have an amplitude value satisfying apredetermined condition; and N angles at which the amplitude values ofthe channel characteristics satisfy the predetermined condition areselected as the N angles at which the channel characteristics aresignificant.

For example, it can be determined whether the channel characteristics ofthe uplink channel from the UE to the BS in the angle domain haveamplitude values satisfying the predetermined condition, and N angles atwhich the amplitude values of the channel characteristics satisfy thepredetermined condition are selected as the N angles at which thechannel characteristics are significant.

Specifically, according to the embodiment of the present disclosure, itis possible to select the top N angles at which the channelcharacteristics of the corresponding channels in the angle domain havelarger amplitude values as the N angles at which the channelcharacteristics are significant.

For example, the top N angles at which the channel characteristics ofthe uplink channel from the UE to the BS in the angle domain have largeramplitude values may be selected as the N angles at which the channelcharacteristics are significant.

The embodiment of the present disclosure described above can bring aboutsome beneficial technical effects. For example, since uplink channelestimation is a step required for uplink data transmission in a mobilecommunication system, determining the channel characteristics of thedownlink channel in the angle domain from the channel state of theuplink channel does not bring about extra resource consumption.

According to still another embodiment of the present disclosure, channelstates of channels between a plurality of antennas of a firstcommunication apparatus (e.g., a BS) and a second communicationapparatus (e.g., a UE) corresponds to channel states of channels fromthe multiple antennas of the first communication apparatus (e.g., a BS)to the second communication apparatus (e.g., a UE). In addition, thechannel characteristic determination unit 621 in the processing circuit620 of the electronic device 600 used for the first communicationapparatus having multiple antennas may also be configured to: based onchannel states of channels from the multiple antennas of the firstcommunication apparatus (e.g., a BS) to the second communicationapparatus (e.g., a UE), determine channel characteristics of a firstchannel (e.g., the downlink channel) in the angle domain.

Specifically, channel estimation of the first channel (e.g., thedownlink channel) from the first communication apparatus (e.g., a BS) tothe second communication apparatus (e.g., a UE) may be performedperiodically using conventional orthogonal pilot signals, and accordingto channel state of the first channel (e.g., the downlink channel) fedback from the second communication apparatus (e.g., a UE) to the firstcommunication apparatus (e.g., a BS), channel characteristics of thefirst channel (e.g., the downlink channel) from the first communicationapparatus (e.g., a BS) to the second communication apparatus (e.g., aUE) in the angle domain are determined. Below, an example of a processflow of determining channel characteristics of a channel between a BSand a UE in the angle domain will be described in detail with referenceto FIG. 10.

FIG. 10 is a diagram illustrating an example of a process flow ofdetermining channel characteristics in the angle domain of a channelbetween a BS and a UE according to an embodiment of the presentdisclosure.

As shown in FIG. 10, in step 101, conventional orthogonal pilot signalsare designed using a conventional orthogonal pilot design method. Forexample, the time domain orthogonal pilot signals shown in FIG. 2, thefrequency domain orthogonal pilot signals shown in FIG. 3, thetime-frequency two-dimensional orthogonal pilot signals shown in FIG. 4,or the code orthogonal pilot signals shown in FIG. 5 may be used.

In step 102, conventional orthogonal pilot signals are transmitted fromthe BS to the UE, and a channel state fed back from the UE is receivedto determine the downlink channel. That is, downlink channel estimationis performed using conventional orthogonal pilot signals to obtain thefed-back channel state of the downlink channel.

In step 103, channel characteristics of the downlink channel from the BSto the UE in the angle domain may be determined according to the channelstate of the downlink channel fed back from the UE to the BS.

It should be noted that the above embodiments examplarily show twomethods of determining channel characteristics of a first channel (e.g.,a downlink channel) from a first communication apparatus (e.g., a BS) toa second communication apparatus (e.g., a UE) in the angle domain.However, the present disclosure is not limited to the above two methods,and other methods may also be used to determine channel characteristicsof a first channel (e.g., a downlink channel) from a first communicationapparatus (e.g., a BS) to a second communication apparatus (e.g., a UE)in the angle domain.

Once channel states of channels between multiple antennas of the firstcommunication apparatus (e.g., a BS) and the second communicationapparatus (e.g., a UE) are obtained, a transformation may be performedon the channel states of the channels between the multiple antennas ofthe first communication apparatus (e.g., a BS) and the secondcommunication apparatus (e.g., a UE) to obtain channel characteristicsof corresponding channels in the angle domain. For example, once achannel state of the downlink channel from the BS to the UE is obtained,the channel state of the downlink channel from the BS to the UE may betransformed to obtain channel characteristics of the downlink channelfrom the BS to the UE in the angle domain.

According to an embodiment of the present disclosure, N angles at whichchannel characteristics are significant are selected from the angledomain based on the channel characteristics of corresponding channels inthe angle domain, where N is a natural number greater than or equal to1, the number of pilot signals in the first set of pilot signals isgreater than or equal to N, and the first set of pilot signals are usedfor the N angles, respectively.

For example, based on channel characteristics of the downlink channelfrom the BS to the UE in the angle domain, the N angles at which channelcharacteristics are significant can be selected from the angle domain,where N is a natural number greater than or equal to 1, the number ofthe first set of pilot signals is greater than or equal to N, and thefirst set of pilot signals are used for the N angles, respectively.

Specifically, according to the embodiment of the present disclosure, itcan be determined whether channel characteristics of correspondingchannels in the angle domain have amplitude values satisfying apredetermined condition; and N angles at which the amplitude values ofthe channel characteristics satisfy the predetermined condition areselected as the N angles at which the channel characteristics aresignificant.

For example, it can be determined whether channel characteristics ofdownlink channels from the BS to the UE in the angle domain haveamplitude values satisfying the predetermined condition, and N angles atwhich the amplitude values of the channel characteristics satisfy thepredetermined condition are selected as the N angles at which thechannel characteristics are significant.

Specifically, according to the embodiment of the present disclosure, itis possible to select the top N angles at which the channelcharacteristics of the corresponding channels in the angle domain havelarger amplitude values as the N angles at which the channelcharacteristics are significant.

For example, the top N angles at which the channel characteristics ofthe downlink channel from the BS to the UE in the angle domain havelarger amplitude values may be selected as the N angles at which thechannel characteristics are significant.

After a preset period, operations of steps 104 to 106 that are the sameas the operations of steps 101 to 103 are repeatedly performed, whosedetail will not be repeated herein. It should be noted that a period fortransmitting conventional orthogonal pilot signals depends on a changingrate of a channel. For example, the period for transmitting theconventional orthogonal pilot signals may be set to several times achannel coherence time.

In the embodiments of the present disclosure described above, the valueof N is determined based on angular spread status of the channelsbetween the multiple antennas of the first communication apparatus(e.g., a BS) and the second communication apparatus (e.g., a UE), thenumber of antennas of the first communication apparatus (e.g., a BS)and/or the number of available pilot signals.

More specifically, the value of N is directly proportional to theangular spread status of the channels between the multiple antennas ofthe first communication apparatus (e.g., a BS) and the secondcommunication apparatus (e.g., a UE), the number of antennas of thefirst communication apparatus (e.g., a BS) and/or the number ofavailable pilot signals.

For example, the value of N may be

${\left\lbrack {\frac{2\; \sigma}{180}M} \right\rbrack \mspace{14mu} {{or}\mspace{14mu}\left\lbrack {\frac{4\; \sigma}{180}M} \right\rbrack}},$

where σ is the standard deviation of angular spread status of channelsbetween the multiple antennas of the first communication apparatus(e.g., a BS) and the second communication apparatus (e.g., a UE), M isthe number of antennas of the first communication apparatus (e.g., aBS), “[⋅]” denotes rounding operation.

In the above embodiments of the present disclosure, the transformationperformed on channel states of channels between the multiple antennas ofthe first communication apparatus (e.g., a BS) and the secondcommunication apparatus (e.g., a UE) may be based on Fourier transform,so as to achieve a transformation from a wireless physical channel to anangle domain channel. That is, the transformation performed on thechannel state of the uplink channel or that of the downlink channelbetween the BS and the UE may be based on Fourier transform.

More specifically, the transformation described above may be FastFourier Transform (FFT), and a transformation matrix adopted by FFT isdetermined based on the type of the multiple antennas of the firstcommunication apparatus (e.g., a BS).

According to an embodiment of the present disclosure, if multipleantennas of the first communication apparatus (e.g., a BS) are antennasin a uniform linear array, the transformation matrix adopted by FFT isan M×M discrete Fast Fourier transformation matrix, where M is thenumber of antennas of the first communication apparatus (e.g., a BS),and M is a natural number greater than or equal to 1.

For example, an element of the p-th row and the q-th column in the aboveM×M discrete Fast Fourier transformation matrix F can be expressed as:

$\lbrack F\rbrack_{p,q} = {\frac{1}{\sqrt{M}} \times e^{{{- j}\; 2\pi \frac{{({p - 1})}{({q - 1})}}{M}}\;}}$

According to an embodiment of the present disclosure, if the multipleantennas of the first communication apparatus (e.g., a BS) are antennasin a uniform planar array, the transformation matrix adopted by FFT isFW⊗FH, where FW is a W×W discrete Fast Fourier transformation matrix,and FH is a H×H discrete Fast Fourier transformation matrix, a denotesKronecker product, W and H represent the numbers of antennas of thefirst communication apparatus (e.g., a BS) in the horizontal andvertical directions respectively, which satisfy W×H=M, in which M is thenumber of antennas of the first communication apparatus (e.g., a BS),and M, W, and H all are natural numbers greater than or equal to 1.

For example, an element of the p-th row and q-th column in the W×Wdiscrete Fast Fourier transformation matrix F_(W) may be:

$\left\lbrack F_{W} \right\rbrack_{p,q} = {\frac{1}{\sqrt{W}} \times e^{{- j}\; 2\; \pi \frac{{({p - 1})}{({q - 1})}}{w}}}$

Similarly, for example, an element of the p-th and q-th columns in theH×H discrete Fast Fourier transformation matrix F_(H) may be:

$\left\lbrack F_{H} \right\rbrack_{p,q} = {\frac{1}{\sqrt{H}} \times e^{{- j}\; 2\; \pi \frac{{({p - 1})}{({q - 1})}}{H}}}$

In addition, in the embodiment described above with reference to steps801 and 802 in FIG. 8, that is, in the case that the channel states ofthe channels between the multiple antennas of the first communicationapparatus (e.g., a BS) and the second communication apparatus (e.g., aUE) correspond to the channel states of the channels from the secondcommunication apparatus (e.g., a UE) to the first communicationapparatus (a BS), indexes of N angles at which channel characteristicsof the second channel (e.g., the uplink channel) in the angle domain aresignificant may be corrected based on an offset between transmissionfrequencies of a first channel (e.g., a downlink channel) and a secondchannel (e.g., an uplink channel), to determine indexes of N angles atwhich channel characteristics of the first channel (e.g., the downlinkchannel) in the angle domain are significant.

In addition, according to an embodiment of the present disclosure, ifthe offset between the transmission frequencies of the first channel(e.g., the downlink channel) and the second channel (e.g., the uplinkchannel) does not satisfy a predetermined correction condition, theindexes of the N angles at which the channel characteristics of thesecond channel (e.g., the uplink channel) in the angle domain aresignificant are directly determined as the indexes of the N angles atwhich the channel characteristics of the first channel (e.g., thedownlink channel) in the angle domain are significant.

According to an embodiment of the present disclosure, the abovedescribed predetermined correction condition may also depend on the typeof the multiple antennas of the first communication apparatus (e.g., aBS).

For example, according to an embodiment of the present disclosure, ifthe multiple antennas of the first communication apparatus (e.g., a BS)are antennas in a uniform linear array, it is determined whether anoffset between the transmission frequencies of the first channel (e.g.,the downlink channel) and the second channel (e.g., the uplink channel)satisfies, for example, the following predetermined correctioncondition:

Δf×M>f ₁

Where, Δf is the absolute value of the difference between thetransmission frequency f₁ of the first channel (e.g., the downlinkchannel) and the transmission frequency f₂ of the second channel (e.g.,the uplink channel), and M is the number of antennas of the firstcommunication apparatus (e.g., a BS), M is a natural number greater thanor equal to 1.

As another example, according to an embodiment of the presentdisclosure, if the multiple antennas of the first communicationapparatus (e.g., a BS) are antennas in a uniform planar array, it isdetermined whether an offset between the transmission frequencies of thefirst channel (e.g., the downlink channel) and the second channel (e.g.,the uplink channel) satisfies, for example, the following predeterminedcorrection condition:

Δf×max(W,H)>f ₁

Where, Δf is the absolute value of the difference between thetransmission frequency f1 of the first channel (e.g., the downlinkchannel) and the transmission frequency f2 of the second channel (e.g.,the uplink channel), W and H represent the numbers of antennas of thefirst communication apparatus (for example, base station) in thehorizontal direction and the vertical direction respectively, andsatisfy W×H=M, in which M is the number of antennas of the firstcommunication apparatus (e.g., BS), M, W, and H all are natural numbersgreater than or equal to 1, and max(W, H) is the maximum of W and H.

According to an embodiment of the present disclosure, the abovecorrection performed on the indexes of the N angles at which the channelcharacteristics of the second channel (e.g., the uplink channel) in theangle domain are significant may depend on the type of the multipleantennas of the first communication apparatus (e.g., a BS).

For example, according to an embodiment of the present disclosure, ifthe multiple antennas of the first communication apparatus (e.g., a BS)are antennas in a uniform linear array, the indexes of the N angles atwhich the channel characteristics of the second channel (for example,the uplink channel) in the angle domain are significant can be correctedaccording to, for example, the following equation:

$p_{i}^{1} = \left\{ \begin{matrix}{\left\lbrack {\frac{\lambda^{2}}{\lambda^{1}}p_{i}^{2}} \right\rbrack,{0 \leq p_{i}^{2} < \frac{M}{2}}} \\{\left\lbrack {M - {\frac{\lambda^{2}}{\lambda^{1}}\left( {M - p_{i}^{2}} \right)}} \right\rbrack,{\frac{M}{2} \leq p_{i}^{2} < M}}\end{matrix} \right.$

where p_(i) ¹ is the index of i-th angle among the N angles at whichchannel characteristics of the first channel (e.g., the downlinkchannel) in the angle domain are significant, and p_(i) ² is the indexof i-th angle among the N angles at which channel characteristics of thesecond channel (e.g., the uplink channel) in the angle domain aresignificant, i is a natural number greater than or equal to 1, 1≤i≤N, λ¹and λ² are transmission wavelengths of the first channel (e.g., thedownlink channel) and the second channel (e.g., the downlink channel),respectively, M is the number of antennas of the first communicationapparatus (e.g., a BS), and [⋅] denotes rounding operation.

As another example, according to an embodiment of the presentdisclosure, if the multiple antennas of the first communicationapparatus (e.g., a BS) are antennas in a uniform planar array, theindexes of the N angles at which channel characteristics of the secondchannel (for example, the uplink channel) in the angle domain aresignificant can be corrected according to, for example, the followingequation:

$x_{i}^{1} = \left\{ {{\begin{matrix}{\left\lbrack {\frac{\lambda^{2}}{\lambda^{1}}x_{i}^{2}} \right\rbrack,{0 \leq x_{i}^{2} < \frac{W}{2}}} \\{\left\lbrack {W - {\frac{\lambda^{2}}{\lambda^{1}}\left( {W - x_{i}^{2}} \right)}} \right\rbrack,{\frac{W}{2} \leq x_{i}^{2} < W}}\end{matrix}y_{i}^{1}} = \left\{ \begin{matrix}{\left\lbrack {\frac{\lambda^{2}}{\lambda^{1}}y_{i}^{2}} \right\rbrack,{0 \leq y_{i}^{2} < \frac{H}{2}}} \\{\left\lbrack {H - {\frac{\lambda^{2}}{\lambda^{1}}\left( {H - y_{i}^{2}} \right)}} \right\rbrack,{\frac{H}{2} \leq y_{i}^{2} < H}}\end{matrix} \right.} \right.$

where x_(i) ¹ and y_(i) ¹ are coordinates of the index p_(i) ¹ of thei-th angle among the N angles at which channel characteristics of thefirst channel (e.g., the downlink channel) in the angle domain aresignificant. x_(i) ² and y_(i) ² are coordinates of the index p_(i) ² ofthe i-th angle among the N angles at which channel characteristics ofthe second channel (e.g., the uplink channel) in the angle domain aresignificant. x_(i) ²=mod(p_(i) ², W), y_(i) ²=(p_(i) ²−x_(i) ²)/W, [⋅]denotes rounding operation, mod(a,b) denotes an operation for theremainder of a divided by b, W and H respectively denote the numbers ofantennas of the first communication apparatus (e.g., a BS) in thehorizontal direction and in the vertical direction, and satisfy W×H=M,in which i is a natural number greater than or equal to 1, 1≤i≤N, λ¹ andλ² are transmission wavelengths of the first channel (e.g., the downlinkchannel) and the second channel (e.g., the downlink channel)respectively, M is the number of antennas of the first communicationapparatus.

In addition, in a scenario where there is no requirement for highaccuracy of the system, instead of determining whether the indexes needto be corrected according to the above predetermined correctioncondition, the indexes of angle domain ports at which channelcharacteristics of the uplink channel in the angle domain aresignificant may be directly used as the indexes of angle domain ports atwhich channel characteristics of the downlink channel in the angledomain are significant.

Below, an example of determining the channel characteristics of thedownlink channel in the angle domain from the channel state of theuplink channel will be described with reference to FIGS. 13A, 13B to15A, and 15B. It is assumed that the number M of antennas provided forthe BS is 8, the number K of antennas provided for the UE is 3, thetransmission frequency of the downlink channel is f₁ the transmissionfrequency of the uplink channel is f₂, and the transmission frequency f₁of the downlink channel and the transmission frequency f₂ of the uplinkchannel satisfy f₂=0.9*f₁. In addition, it is also assumed that theantennas provided for the BS are antennas in a uniform linear array.

FIG. 13A is a diagram illustrating a channel state of an uplink channelof a first UE according to an embodiment of the present disclosure. Asshown in FIG. 13A, the horizontal axis indicates antenna port indexes,and the vertical axis indicates channel characteristic amplitude values.As shown in FIG. 13A, for the uplink channel of the first UE, channelstate vector element U₁₀ on antenna port0=(−0.445292748915722−0.0895391682772950i), and its channelcharacteristic amplitude is 0.454205784741575; channel state vectorelement U₁₁ on antenna port 1=(0.429935240361251−0.301353644108254254i),and its channel characteristic amplitude is 0.525031741632647; channelstate vector element U₁₂ on antenna port2=(−0.0772191708737074+0.493579638426503i), and its channelcharacteristic amplitude is 0.499583486336028; channel state vectorelement U₁₃ on the antenna port3=(−0.245440920746513−0.300407910708885i), and its channelcharacteristic amplitude is 0.387925454686043; channel state vectorelement U₁₄ on the antenna port4=(0.227983908018620−0.0196887267967956i), and its channelcharacteristic amplitude is 0.228832489560040; channel state vectorelement U₁₅ on the antenna port5=(0.0125163370492662+0.103088869741354i), and its channelcharacteristic amplitude is 0.103845913533854; channel state vectorelement U₁₆ on the antenna port6=(−0.125417988465446+0.0645631308891503i), and its channelcharacteristic amplitude is 0.141060517867078; and channel state vectorelement U₁₇ on the antenna port7=(0.00129973639612804−0.186871389251782i), and its channelcharacteristic amplitude is 0.186875909190004. Therefore, the channelstate of the upstream channel of the first UE can be represented asvector U₁:

$U_{1} = \begin{bmatrix}U_{10} \\U_{11} \\U_{12} \\U_{13} \\U_{14} \\U_{15} \\U_{16} \\U_{17}\end{bmatrix}$

Since it is assumed that the antennas provided for the BS are antennasin a uniform linear array as described above, each element[F]p,q in a8×8 discrete Fast Fourier Transform matrix F employed by FFT isdetermined according to the following equation:

$\lbrack F\rbrack_{p,q} = e^{{- j}\; 2\; \pi \frac{{({p - 1})}{({q - 1})}}{8}}$

where, p and q both are natural numbers greater than or equal to 1 andless than or equal to 8.

By multiplying the 8×8 discrete Fast Fourier Transform matrix F by thechannel state vector U₁ of the uplink channel of the first UE, a channelcharacteristic vector A₁ of the uplink channel of the first UE in theangle domain can be obtained. That is, the channel characteristic vectorA₁ of the uplink channel of the first UE in the angle domain can beexpressed as follows:

$A_{1} = {{F \times U_{1}} = {{F \times \begin{bmatrix}U_{10} \\U_{11} \\U_{12} \\U_{13} \\U_{14} \\U_{15} \\U_{16} \\U_{17}\end{bmatrix}} = \begin{bmatrix}A_{10} \\A_{11} \\A_{12} \\A_{13} \\A_{14} \\A_{15} \\A_{16} \\A_{17}\end{bmatrix}}}$

where, A₁₀=(−0.0783600203933173−0.0836610560030985i), with an amplitudeof 0.114627505807265; A₁₁=(−0.0498138727191462−0.157132775443158i), withan amplitude of 0.164839713157204;A₁₂=(0.0969948426938652−0.478698360054164i) with an amplitude of0.488426165789420; A₁₃=(−0.685254134667091+0.0224019315173863i) with anamplitude of 0.685620212372749;A₁₄=(−0.218586644105906+0.401091807756179i), with an amplitude of0.456787433310726; A₁₅=(−0.122904135293104+0.0736593438377662i), with anamplitude of 0.143286864041181;A₁₆=(−0.107369288214900+0.00679603770056940i), with an amplitude of0.107584153945652; and A₁₇=(−0.0941848367864231−0.0377119415941945i),with an amplitude of 0.101454295223461.

It can be seen that indexes of angle domain ports corresponding to thetop 3 channel characteristics of the uplink channel of the first UE inthe angle domain with larger amplitude values (0.488426165789420,0.685620212372749 and 0.456787433310726) are 2, 3 and 4 respectively.

In addition, as it is assumed that the antennas provided for the BS areantennas in a uniform linear array as described above, it can bedetermined, according to the following predetermined correctioncondition, whether the indexes (2, 3 and 4) of the three angle domainports with significant channel characteristics of the uplink channel ofthe first UE in the angle domain need to be corrected:

Δf×M>f ₁

Since Δf×M=(f₁−f₂)×M=(f₁−0.9f₁)×8=0.8f₁<f₁ as described above, there isno need to correct the indexes (2, 3 and 4) of the three angle domainports with significant channel characteristics of the uplink channel ofthe first UE in the angle domain. That is, the indexes (2, 3 and 4) ofthe three angle domain ports with significant channel characteristics ofthe uplink channel of the first UE in the angle domain can be directlydetermined as indexes (2, 3 and 4) of three angle domain ports withsignificant channel characteristics of the downlink channel of the firstUE in the angle domain.

Further, in a scenario where there is no requirement for high accuracyof the system, instead of determining whether correction needs to beperformed according to the above predetermined correction condition, theindexes (2, 3 and 4) of angle domain ports with significant channelcharacteristics of the uplink channel of the first UE in the angledomain may be directly used as the indexes (2, 3 and 4) of angle domainports with significant channel characteristics of the downlink channelof the first UE in the angle domain.

FIG. 13B is a diagram illustrating the actual channel characteristics ofthe downlink channel of a first UE in the angle domain according to anembodiment of the present disclosure. As shown in FIG. 13B, the indexesof angle domain ports corresponding to the top 3 channel characteristicswith larger amplitude values in the downlink channel of the first UE inthe angle domain are also 2, 3 and 4 respectively. Thus, the indexes ofangle domain ports corresponding to the top 3channel characteristicshaving larger amplitude values in the downlink channel of the first UEin the angle domain calculated in the above manner are consistent withthe indexes of angle domain ports corresponding to the top 3 actualchannel characteristics having larger amplitude values in the downlinkchannel of the first UE in the angle domain.

FIG. 14A is a diagram illustrating a channel state of the uplink channelof a second UE according to an embodiment of the present disclosure.FIG. 14B is a diagram illustrating actual channel characteristics of thedownlink channel of the second UE in the angle domain according to anembodiment of the present disclosure. Similar to FIG. 13A, it can bedetermined that the indexes of angle domain ports corresponding to thetop 3 channel characteristics having larger amplitude values in theuplink channel of the second UE in the angle domain are 1, 2 and 5respectively.

In addition, as it is assumed that the antennas provided for the BS areantennas in a uniform linear array as described above, it can bedetermined according to the following predetermined correction conditionwhether the indexes (1, 2 and 5) of the three angle domain ports withsignificant channel characteristics of the uplink channel of the secondUE in the angle domain need to be corrected:

Δf×M>f ₁

As described above, Δf×M=(f₁−f₂)×M=(f₁−0.9f₁)×8=0.8f₁<f₁, there is noneed to correct the indexes (1, 2 and 5) of the three angle domain portswith significant channel characteristics of the uplink channel of thesecond UE in the angle domain. That is, the indexes (1, 2 and 5) ofthree angle domain ports with significant channel characteristics of theuplink channel of the second UE in the angle domain can be directlydetermined as the indexes (1, 2 and 5) of three angle domain ports withsignificant channel characteristics of the downlink channel of thesecond UE in the angle domain.

Further, similarly, in a scenario where there is no requirement for highaccuracy of the system, instead of determining whether correction needsto be performed according to the above predetermined correctioncondition, the indexes (1, 2 and 5) of angle domain ports withsignificant channel characteristics of the uplink channel of the secondUE in the angle domain may be directly used as indexes (1, 2 and 5) ofangle domain ports with significant channel characteristics of thedownlink channel of the second UE in the angle domain.

As shown in FIG. 14B, the indexes of antenna ports corresponding to thetop 3 channel characteristics having larger amplitude values in thedownlink channel of the second UE in the angle domain are also 1, 2 and5 respectively. Thus, the indexes of angle domain ports corresponding tothe top 3 channel characteristics having larger amplitude values in thedownlink channel of the second UE in the angle domain calculated in theabove manner are consistent with the indexes of angle domain portscorresponding to the top 3actual channel characteristics having largeramplitude values in the downlink channel of the second UE in the angledomain.

FIG. 15A is a diagram illustrating a channel state of an uplink channelof a third UE according to an embodiment of the present disclosure. FIG.15B is a diagram illustrating actual channel characteristics of thedownlink channel of the third UE in the angle domain according to anembodiment of the present disclosure. Similar to FIG. 13A, it can bedetermined that the indexes of angle domain ports corresponding to thetop 3channel characteristics having larger amplitude values in theuplink channel of the third UE in the angle domain are 4, 5 and 6respectively.

In addition, as it is assumed that the antennas provided for the BS areantennas in a uniform linear array as described above, it can bedetermined according to the following predetermined correction conditionwhether the indexes (4, 5 and 6) of the three angle domain ports withsignificant channel characteristics of the uplink channel of the thirdUE in the angle domain need to be corrected:

Δf×M>f ₁

As described above, since Δf×M=(f₁−f₂)×M=(f₁−0.9f₁)×8=0.8f₁<f₁, there isno need to correct the indexes (4, 5 and 6) of the three angle domainports with significant channel characteristics of the uplink channel ofthe third UE in the angle domain. That is, the indexes (4, 5 and 6) ofthe three angle domain ports with significant channel characteristics ofthe uplink channel of the third UE in the angle domain can be directlydetermined as the indexes (4, 5 and 6) of the three angle domain portswith significant channel characteristics of the downlink channel of thethird UE in the angle domain.

Further, similarly, in a scenario where there is no requirement for highaccuracy of the system, instead of determining whether correction needsto be performed according to the above predetermined correctioncondition, the indexes (4, 5 and 6) of the angle domain ports withsignificant channel characteristics of the uplink channel of the thirdUE in the angle domain may be directly used as the indexes (4, 5 and 6)of the angle domain ports with significant channel characteristics ofthe downlink channel of the third UE in the angle domain.

As shown in FIG. 15B, indexes of angle domain ports corresponding to thetop 3 channel characteristics having larger amplitude values in thedownlink channel of the third UE in the angle domain are also 4, 5 and 6respectively. Thus, the indexes of the angle domain ports correspondingto the top 3 channel characteristics having larger amplitude values inthe downlink channel of the third UE in the angle domain calculated inthe above manner are consistent with the indexes of the angle domainports corresponding to the top 3 actual channel characteristics havinglarger amplitude values in the downlink channel of the third UE in theangle domain.

Referring back to FIG. 8, in step 8004, a first set of pilot signalsused in the angle domain is determined based on the determined channelcharacteristics of the first channel (e.g., the downlink channel) in theangle domain, wherein the pilot signals in the first set of pilotsignals are orthogonal to each other.

According to the MIMO channel model provided by the 3GPP standardizationorganization (see 3GPP TR 36.814 V9.0.0, “Further advancements forE-UTRA physical layer aspects”, March 2010), in the Urban Macro-cellscenario, since the height of the macro base station is often high andthe scatterers are often distributed around the user, channel anglespreading is small, resulting in sparsity of the channels in the angledomain.

Therefore, when designing pilot signals in the angle domain, the sparsecharacteristics of the channels in the angle domain can be utilized toonly place orthogonal pilot signals in positions in the angle domainwhere the channel characteristics are significant, and set zero to otherpositions than that having significant channel characteristics in theangle domain, so that the overhead of pilot signal can be reduced, andin turn the overhead of channel estimation can be reduced.

For example, suppose there is only one UE (a first user equipment) in awireless communication system. Returning back to FIGS. 13A and 13B,since it has been determined that the indexes of the three angle domainports with significant channel characteristics of the uplink channel ofthe first UE in the angle domain are 2, 3, and 4, orthogonal pilotsignals can be placed at these three angle domain ports (2, 3 and 4)with significant channel characteristics in the angle domain, and otherangle domain ports (0,1, 5, 6 and 7) in the angle domain are set tozero. Therefore, the overhead of pilot signal can be reduced, and inturn the overhead of channel estimation can be reduced.

According to an embodiment of the present disclosure, in a case where afirst communication apparatus (e.g., a BS) communicates with multiplesecond communication apparatus (e.g., multiple UEs), a first set ofpilot signals used in the angle domain can be determined for themultiple second communication apparatus (e.g., multiple UEs), whereinrespective pilot signals in the first set of pilot signals areorthogonal to each other with respect to angles as a union of N angleswith significant channel characteristics in the angle domain of acorresponding first channel (e.g., the downlink channel) from the firstcommunication apparatus (e.g., a BS) to each (e.g., each UE) of themultiple second communication apparatus (e.g., multiple UEs), wherein Nis a natural number greater than or equal to 1.

Below an example of an angle domain completely orthogonal pilot signalsequence according to an embodiment of the present disclosure isdescribed with reference to FIG. 16, which is a schematic diagramillustrating an example of an angle domain completely orthogonal pilotsignal sequence according to an embodiment of the present disclosure.

Assume that Ω_(k) ^(DL) is a set of indexes of angle domain ports havingsignificant channel characteristics of the downlink channel of the k-thUE in the angle domain, Ω=∪_(k=0) ^(K−1)Ω_(k) ^(DL) is a union of theset of indexes of angle domain ports having significant channelcharacteristics of the downlink channel of all the UEs in the angledomain.

In order to obtain an angle domain completely orthogonal pilot signalsequence, orthogonal pilot signals must be allocated for all angledomain ports whose indexes are included in the set Ω, and the otherangle domain ports do not send pilot signals. The angle domaincompletely orthogonal pilot signal sequence can ensure that angle domainchannel estimations cannot interfere with each other in the case wherethe antenna angles of arrival of different UEs, that is, the set ofindexes of the angle domain ports having significant channelcharacteristics of the downlink channel of different UEs in the angledomain, are different.

Assume that Nc is the number of orthogonal pilot signals required in theangle domain completely orthogonal pilot signal sequence (ie, the firstset of pilot signals), that is, the overhead of downlink channelestimation. Due to the distribution randomness of the set of indexes ofangle domain ports having significant channel characteristics of thedownlink channel of each UE in the angle domain, there is Nc=min{KN,M},where K is the number of UEs, N is the size of the set of angle domainports having significant channel characteristics of the downlink channelof the UE in the angle domain, where M is the number of antennasprovided for the BS, and min( ) is a function returning a minimum valueof its parameters, K, N, and M all are natural numbers greater than orequal to 1. In other words, when the number of orthogonal pilot signalsis Nc, the number of UEs that can be supported in the communicationsystem at most is

${K = \left\lfloor \frac{N_{c}}{N} \right\rfloor},$

where └⋅┘ denotes the rounding-down function.

As shown by the dark blocks in FIG. 16, it is assumed that the set Ω₀^(DL) of indexes of angle domain ports having significant channelcharacteristics of the downlink channel of the first UE in the angledomain is (2, 3 and 4), the set Ω₁ ^(DL) of indexes of angle domainports having significant channel characteristics of the downlink channelof the second UE in the angle domain is (1, 2 and 5), and the set Ω₂^(DL) of indexes of angle domain ports having significant channelcharacteristics of the downlink channel of the third UE in the angledomain is (4, 5 and 6). Therefore, a union of the sets of indexes ofangle domain ports having significant channel characteristics of thedownlink channel of all the UEs in the angle domain is Ω=∪_(k=0) ²Ω_(k)^(DL)=(1,2,3,4,5,6).

Thus, a completely orthogonal pilot signal sequence (S0, S1, S2, S3, S4,S5) can be allocated for the angle domain ports 1 to 6, and the otherangle domain ports 0 and 7 are not used to send pilot signals, so thatthe angle domain completely orthogonal pilot signal sequence (i.e., thefirst set of pilot signals) is (0, S0, S1, S2, S3, S4, S5, 0).

An example of allocating transmission resources for angle domaincompletely orthogonal pilot signals according to an embodiment of thepresent disclosure will be described below with reference to FIG. 18.FIG. 18 is a schematic diagram illustrating an example of allocatingtransmission resources for angle domain completely orthogonal pilotsignals according to an embodiment of the present disclosure.

According to the embodiment of the present disclosure, transmissionresources are allocated for the pilot signals in the determined firstset of pilot signals, and the number of transmission resources isproportional to the number of pilot signals in the determined first setof pilot signals.

As shown in FIG. 18, no pilot signals are sent on the angle domain ports0 and 7, and an orthogonal pilot signal S0=[1, 0, 0, 0, 0, 0] istransmitted on the angle domain port 1, an orthogonal pilot signalS1=[0, 1, 0, 0, 0, 0] is transmitted on the angle domain port 2, anorthogonal pilot signal S2=[, 0, 1, 0, 0, 0] is transmitted on the angledomain port 3, an orthogonal pilot signal S3=[0, 0, 0, 1, 0, 0] istransmitted on the angle domain port 4, an orthogonal pilot signalS4=[0, 0, 0, 0, 1, 0] is transmitted on the angle domain port 5, and anorthogonal pilot signal S5=[0, 0, 0, 0, 0, 1] is transmitted on theangle domain port 6. Therefore, since the number of pilot signals S0 toS5 in the first set of pilot signals is 6, the number of requiredtransmission resources is 6.

According to another embodiment of the present disclosure, in a casewhere a first communication apparatus (e.g., a BS) communicates withmultiple second communication apparatus (e.g., multiple UEs), a firstset of pilot signals used in the angle domain can be determined for themultiple second communication apparatus (e.g., multiple UEs). In thecase where the number of pilot signals in the first set of pilot signalsis minimum, respective pilot signal in the first set of pilot signalsare orthogonal to each other with respect to angles corresponding to Nangles having significant channel characteristics in the angle domain ofa corresponding first channel (e.g., the downlink channel) from thefirst communication apparatus (e.g., a BS) to one of the multiple secondcommunication apparatus (e.g., multiple UEs), where N is a naturalnumber greater than or equal to 1.

An example of an angle domain partially orthogonal pilot signal sequenceaccording to an embodiment of the present disclosure will be describedbelow with reference to FIG. 17. FIG. 17 is a diagram illustrating anexample of an angle domain partially orthogonal pilot signal sequenceaccording to an embodiment of the present disclosure.

In order to obtain an angle domain partially orthogonal pilot signalsequence, for the k-th (1≤k≤K) UE, K is a natural number greater than orequal to 1, orthogonal pilot signals must be allocated for all angledomain ports whose indexes are in Ω_(k) ^(DL), and other angle domainports do not need to send pilot signals. The angle domain partiallyorthogonal pilot signal sequence may introduce some interference, butthe interference is limited to interference from channel coefficientsexcluded from the set of indexes of angle domain ports havingsignificant channel characteristics of the downlink channel of the UE inthe angle domain to channel coefficients in the set of indexes. Due tochannel sparsity in the angle domain, the channel coefficients excludedfrom the set of indexes have smaller amplitude values, so that theinterference is small. Compared to the angle domain completelyorthogonal pilot signal sequence, the angle domain partial orthogonalpilot signal sequence greatly reduces the number of required pilotsignals.

Assume that Ns is the number of orthogonal pilot signals required in theangle domain partially orthogonal pilot signal sequence (ie, the firstset of pilot signals), that is, the overhead of downlink channelestimation. The applicant has found by simulation experiments thatNs=1.5N is a relatively reasonable choice, where N is the size of theset of indexes of angle domain ports having significant channelcharacteristics of the downlink channel of the UE in the angle domain,and N is a natural number greater than or equal to 1.

As shown by the dark blocks in FIG. 17, it is assumed that the set ofindexes Ω₀ ^(DL) of angle domain ports having significant channelcharacteristics of the downlink channel of the first UE in the angledomain is (2, 3 and 4), the set of indexes Ω₁ ^(DL) of angle domainports having significant channel characteristics of the downlink channelof the second UE in the angle domain is (1, 2 and 5), and the set ofindexes Ω₂ ^(DL) of angle domain ports having significant channelcharacteristics of the downlink channel of the third UE in the angledomain is (4, 5 and 6).

A partially orthogonal pilot signal sequence (S0,S1,S2,S0,S2,S1) can beallocated for the angle domain ports 1 to 6, and the other angle domainports 0 and 7 do not send pilot signals, so that the obtained angledomain partially orthogonal pilot signal sequence (i.e., the first setof pilot signals) is (0,S0,S1,S2,S0,S2,S1,0). That is, for the first UE,orthogonal pilot signals S1, S2, and S0 are allocated for the angledomain ports 2, 3, and 4 in the set of indexes Ω₀ ^(DL); for the secondUE, orthogonal pilot signals S0, S1, and S2 are allocated for the angledomain ports 1, 2, and 5 in the set of indexes Ω₁ ^(DL); and for thethird UE, orthogonal pilot signals S0, S2, and S1 are allocated for theangle domain ports 4, 5, and 6 in the set of indexes L.

An example of allocating transmission resources for angle domainpartially orthogonal pilot signals according to an embodiment of thepresent disclosure will be described below with reference to FIG. 19.FIG. 19 is a schematic diagram illustrating an example of allocatingtransmission resources for angle domain partially orthogonal pilotsignals according to an embodiment of the present disclosure.

According to the embodiment of the present disclosure, transmissionresources are allocated for pilot signals in the determined first set ofpilot signals, and the number of transmission resources is proportionalto the number of pilot signals in the determined first set of pilotsignals.

As shown in FIG. 19, no pilot signals are sent on the angle domain ports0 and 7, and an orthogonal pilot signal S0=[1, 0, 0] is transmitted onthe angle domain port 1, an orthogonal pilot signal S1=[0, 1, 0] istransmitted on the angle domain port 2, an orthogonal pilot signalS2=[0, 0, 1] is transmitted on the angle domain port 3, an orthogonalpilot signal S0=[1, 0, 0] is transmitted on the angle domain port 4, anorthogonal pilot signal S2=[0, 0, 0,] is transmitted on the angle domainport 5, and an orthogonal pilot signal S1=[0, 1, 0] is transmitted onthe angle domain port 6. Therefore, since the number of pilot signals S0to S2 in the first set of pilot signals is 3, the number of requiredtransmission resources is 3.

Referring back to FIG. 8, in step 8005, the first set of pilot signalsused in the angle domain is transformed into a second set of pilotsignals (e.g., downlink pilot signals in the antenna domain or wirelessphysical channel) for transmission over the multiple antennas of thefirst communications device (e.g., a BS).

Once the first set of pilot signals used in the angle domain isobtained, it can be transformed to obtain a second set of pilot signals(e.g., downlink pilot signals in the antenna domain or wireless physicalchannel) for transmission over the multiple antennas of the firstcommunications device (e.g., a BS).

In the above described embodiment of the present disclosure, thetransformation performed on the first set of pilot signals used in theangle domain may be based on a Fourier transformation. Morespecifically, the transformation described above may be Fast FourierTransform (FFT), and a transformation matrix adopted by FFT isdetermined according to the type of the multiple antennas of the firstcommunication apparatus (e.g., a BS).

According to an embodiment of the present disclosure, if multipleantennas of the first communication apparatus (e.g., a BS) are antennasin a uniform linear array, the transformation matrix adopted by FFT isan M×M discrete fast Fourier transformation matrix, where M is thenumber of antennas of the first communication apparatus (e.g., a BS),and M is a natural number greater than or equal to 1.

For example, the element in the p-th row and the q-th column in theabove M×M discrete fast Fourier transformation matrix F can be expressedas:

$\lbrack F\rbrack_{p,q} = {\frac{1}{\sqrt{M}} \times e^{{- j}\; 2\; \pi \frac{{({p - 1})}{({q - 1})}}{M}}}$

According to an embodiment of the present disclosure, if the multipleantennas of the first communication apparatus (e.g., a BS) are antennasin a uniform planar array, the transformation matrix adopted by FFT isF_(W)⊗F_(H), where F_(W) is a W×W discrete fast Fourier transformationmatrix, and F_(H) is a H×H discrete fast Fourier transformation matrix,⊗ denotes the Kronecker product, W and H represent the numbers ofantennas of the first communication apparatus (e.g., a BS) in thehorizontal and vertical directions respectively, which satisfy W×H=M, inwhich M is the number of antennas of the first communication apparatus(e.g., a BS), and M, W, and H all are natural numbers greater than orequal to 1.

For example, the element in the p-th row and q-th column in the W×Wdiscrete fast Fourier transformation matrix F_(W) may be:

$\left\lbrack F_{W} \right\rbrack_{p,q} = {\frac{1}{\sqrt{W}} \times e^{{- j}\; 2\; \pi \frac{{({p - 1})}{({q - 1})}}{W}}}$

Similarly, for example, the element of in the p-th and q-th columns inthe H×H discrete fast Fourier transformation matrix F_(H) may be:

$\left\lbrack F_{H} \right\rbrack_{p,q} = {\frac{1}{\sqrt{H}} \times e^{{- j}\; 2\; \pi \frac{{({p - 1})}{({q - 1})}}{H}}}$

An example of performing FFT on the first set of pilot signals used inthe angle domain will be described in detail below.

Taking a FFT transformation of length 4 as an example, the FFT matrixmay be, for example,

$\quad\begin{bmatrix}0.5 & 0.5 & 0.5 & 0.5 \\0.5 & {{- 0.5}i} & {- 0.5} & {0.5i} \\0.5 & {- 0.5} & 0.5 & {- 0.5} \\0.5 & {0.5i} & {- 0.5} & {{- 0.5}i}\end{bmatrix}$

If the angle domain ports 1 and 2 transmit pilot signal 1 at the sametime and other angle domain ports 0 and 3 do not transmit pilot signals,then the pilot signal after FFT transformation transmitted on theantenna ports is:

$\quad{\begin{bmatrix}0.5 & 0.5 & 0.5 & 0.5 \\0.5 & {{- 0.5}i} & {- 0.5} & {0.5i} \\0.5 & {- 0.5} & 0.5 & {- 0.5} \\0.5 & {0.5i} & {- 0.5} & {{- 0.5}i}\end{bmatrix} \times {\quad{\begin{bmatrix}0 \\1 \\1 \\0\end{bmatrix} = {{\begin{bmatrix}0.5 \\{{- 0.5}i} \\{- 0.5} \\{0.5i}\end{bmatrix} + \begin{bmatrix}0.5 \\{- 0.5} \\0.5 \\{- 0.5}\end{bmatrix}} = {\quad\begin{bmatrix}\; & 1 & \; \\{- 0.5} & - & {0.5i} \\\; & 0 & \; \\{- 0.5} & + & {0.5i}\end{bmatrix}}}}}}$

It can be seen that the pilot signal after FFT transformationtransmitted on the antenna ports is equal to the second column of theFFT matrix multiplied by 1, plus its third column multiplied by 1.

Similarly, referring back to FIG. 17, another example of performing FFTon a first set of pilot signals used in the angle domain will bedescribed with the first set of angle domain partially orthogonal pilotsignals (0,S0,S1,S2,S0,S2,S1,0) shown in FIG. 17 as an example.

Specifically, it is assumed that the angle domain partially orthogonalpilot signals are: S0=[1,0,0], S1=0,1,0 and S2=[0,0,1] respectively.

For all the angle domain ports 0 to 7, the downlink pilot signal in theangle domain is

$\overset{\sim}{\Phi} = {\begin{bmatrix}0 \\{S\; 0} \\{S\; 1} \\{S\; 2} \\{S\; 0} \\{S\; 2} \\{S\; 1} \\0\end{bmatrix} = \begin{bmatrix}0 & 0 & 0 \\1 & 0 & 0 \\0 & 1 & 0 \\0 & 0 & 1 \\1 & 0 & 0 \\0 & 0 & 1 \\0 & 1 & 0 \\0 & 0 & 0\end{bmatrix}}$

That is, in the first time slice (the first column in the above matrix{tilde over (Φ)}), a bit 1 is transmitted on the angle domain ports 1and 4, and no pilot signal is transmitted on the other ports 0, 2-3, and5-7; in the second time slice (the second column in the above matrix{tilde over (Φ)}), a bit 1 is transmitted on the angle domain ports 2and 6, and no pilot signal is transmitted on the other ports 0-1, 3-5and 7; in the third time slice (the third column in the above matrix{tilde over (Φ)}), a bit 1 is transmitted on the angle domain ports 3and 5, and no pilot signal is transmitted on the other ports 0-2, 4 and6-7.

Thus, in the first time slice, the signal sent on the antennas is thesum of the second row of the FFT matrix multiplied by 1 and the fifthrow of the FFT matrix multiplied by 1; in the second time slice, thesignal sent on the antennas is the sum of the third row of the FFTmatrix multiplied by 1 and the seventh row of the FFT matrix multipliedby 1; in the third time slice, the signal sent on the antennas is thesum of the fourth row of the FFT matrix multiplied by 1 and the sixthrow of the FFT matrix multiplied by 1.

Referring back to FIG. 8, in step 8006, the second set of pilot signals(for example, downlink pilot signals in the antenna domain or wirelessphysical channel) is sent to the second communication apparatus (e.g., aUE) over the multiple antennas of the first communications device (e.g.,a BS).

In step 8007, channel estimation is performed on the first channel (forexample, the downlink channel) from the first communication apparatus(e.g., a BS) to the second communication apparatus (e.g., a UE) based onthe second set of pilot signals (for example, downlink pilot signals inthe antenna domain or wireless physical channel) from the multipleantennas of the first communications device (e.g., a BS).

Considering a single-cell large-scale antenna system operating in theFDD mode. The BS is equipped with M antennas and serves K single-antennausers. M and K both are natural numbers greater than or equal to 1. Thedownlink channel estimation model can be expressed as:

y=h ^(DLT) Φ+n

where, Φ represents pilot signals transmitted on the antenna ports(associated with a wireless physical channel), and the jth (1≤j≤M) rowof Φ represents the pilot signal transmitted on the jth antenna.

In addition, the channel {tilde over (h)} in the angle domain can bedefined as a FFT transformation of a wireless physical channel h, i.e.,{tilde over (h)}=Fh. Similarly, the pilot signal {tilde over (Φ)} in theangle domain can be defined as an iFFT transformation of the pilotsignal {tilde over (Φ)} transmitted on the wireless physical channel,i.e., {tilde over (Φ)}=F^(H)Φ. Thereby, a downlink channel estimationmodel in the angle domain can be obtained:

y=(F ^(H) {tilde over (h)} ^(DL))^(T)(F{tilde over (Φ)})+n={tilde over(h)} ^(DL,T) {tilde over (Φ)}+n

Therefore, the channel {tilde over (h)} in the angle domain can beestimated from the pilot signal {tilde over (Φ)} in the angle domain,and the wireless physical channel h or the antenna domain channel h canbe reconstructed by an iFFT (inverse FFT) transformation.

According to the downlink channel estimation model in the angle domaindescribed above, the UE may estimate channel coefficients in the angledomain corresponding to each orthogonal pilot signal using a channelestimation method, such as LS, MMSE, etc.

In step 8008, based on a result of the channel estimation performed onthe first channel (for example, the downlink channel) from the firstcommunication apparatus (e.g., a BS) to the second communicationapparatus (e.g., a UE), channel characteristics of the first channel atmultiple angles corresponding to the pilot signals in the first set ofpilot signals, which will be fed back to the first communicationapparatus (e.g., a BS) are determined for channel reconstruction of thefirst channel (for example, the downlink channel).

According to an embodiment of the present disclosure, channelcharacteristics of the first channel (for example, the downlink channel)at multiple angles corresponding to the respective pilot signals in thefirst set of pilot signals may be fed back to the first communicationapparatus (e.g., a BS) in a predetermined order sequentially. Accordingto this embodiment, the first communication apparatus can obtainabundant results of channel estimation and reconstruct a more accuratephysical channel.

For example, taking the angle domain completely orthogonal pilot signalsequence shown in FIG. 16 as an example, the UE sequentially feeds backchannel coefficients corresponding to the orthogonal pilot signals S0,S1, S2, S3, S4, and S5 (that is, indexes 1˜6 of angle domain ports).

As another example, taking the angle domain partially orthogonal pilotsignal sequence shown in FIG. 17 as an example, the UE sequentiallyfeeds back channel coefficients corresponding to the orthogonal pilotsignals S0, S1, S2. As described above, the BS can be aware of someangles having significant channel characteristics corresponding to theUE from uplink channel estimation. In combination with such information,a physical channel can be reconstructed according to the channelcoefficients sequentially fed back by the UE.

According to an embodiment of the present disclosure, significantchannel characteristics in channel characteristics of the first channel(for example, the downlink channel) at multiple angles and indexesidentifiers of pilot signals in the first set of pilot signalscorresponding to the significant channel characteristics can be fed backto the first communication apparatus (e.g., a BS). In this embodiment,the feedback overhead of the second communication apparatus is reduced.

For example, taking the angle domain completely orthogonal pilot signalsequence shown in FIG. 16 as an example, the first UE estimates thatamong the obtained channel coefficients, the channel coefficientscorresponding to the orthogonal pilot signals S1, S2 and S3 have thelargest amplitude values, the first UE may only feed back the channelcoefficients corresponding to the orthogonal pilot signals S1, S2 and S3and the index identifiers of these orthogonal pilot signals S1, S2 andS3.

As another example, taking the angle domain partially orthogonal pilotsignal sequence shown in FIG. 17 as an example, assume that the first UEestimates that, among the obtained channel coefficients, the channelcoefficient corresponding to the orthogonal pilot signal S1 has thelargest amplitude value, the first UE may feed back the channelcoefficient corresponding to the orthogonal pilot signal S1 and feedback the index identifier of the orthogonal pilot signal S1. Asdescribed above, the BS can be aware of some angles having significantchannel characteristics corresponding to a UE from uplink channelestimation. In combination with such information, a physical channel canbe reconstructed based on the most significant channel coefficient fedback by the UE in sequence.

In step 8009, the first channel (for example, the downlink channel) isreconstructed based on the channel characteristics of the first channel(for example, the downlink channel) at multiple angles, which are fedback from the second communication apparatus (e.g., a UE) and correspondto the pilot signals in the first set of pilot signals.

According to the downlink channel estimation model in the angle domaindescribed above y=(F^(H){tilde over (h)}^(DL))^(T)(F{tilde over(Φ)})+n={tilde over (h)}^(DL,T){tilde over (Φ)}+n, a channel {tilde over(h)} in the angle domain can be estimated from the pilot signal {tildeover (Φ)} in the angle domain, and a wireless physical channel h can bereconstructed through an iFFT transformation.

Specifically, after the feedback step, the BS obtains channelcoefficients fed back by each UE and orthogonal pilot signalscorresponding to the channel coefficients. Because the orthogonal pilotsignals are allocated based on a set of indexes of angle domain portshaving significant channel characteristics of the downlink channel ofeach UE in the angle domain, for each UE, the BS can obtain the indexesof angle domain ports corresponding to each feedback channelcoefficient. When the downlink channel of each UE is reconstructed, thevalue of each angle domain port is set to a corresponding feedbackchannel coefficient, or zero if no corresponding feedback channelcoefficient is available, to obtain a reconstructed channel in the angledomain.

Finally, iFFT is performed on a vector of the reconstructed channel inthe angle domain to obtain a reconstructed downlink channel of the UE.

4. CONFIGURATION OF THE ANGLE DOMAIN ORTHOGONAL PILOT SYSTEM ACCORDINGTO AN EMBODIMENT OF THE PRESENT DISCLOSURE

An example of the configuration of the angle domain orthogonal pilotsystem according to an embodiment of the present disclosure will bedescribed below with reference to FIG. 11. FIG. 11 is a diagram showingan example of the configuration of the angle domain orthogonal pilotsystem according to an embodiment of the present disclosure.

As shown in FIG. 11, an angle domain downlink channel characteristicdetermining module may be configured to estimate a set of indexes ofangle domain ports having significant channel characteristics of thedownlink channel of each UE in the angle domain; a pilot allocationmodule may be configured to allocate orthogonal pilot signals for eachangle domain port according to the set of indexes of angle domain portshaving significant channel characteristics of the downlink channel ofeach UE in the angle domain, which are then sent to each UE viacorresponding RF links and antenna ports after FFT transformation. Itshould be noted that the angle domain channel shown in FIG. 11represents an equivalent channel between the angle domain ports andvarious UEs.

In addition, the RF links shown in FIG. 11 correspond to the antennaports one by one, but the present disclosure is not limited to thisexample. For example, the present disclosure can also be applied to anexample in which one RF link connects a plurality of antennas, and inthis case, a plurality of antennas connected by the same RF link can beregarded as one antenna in the example of the present disclosure.

5. EXEMPLARY FLOW OF A COMMUNICATION METHOD ACCORDING TO AN EMBODIMENTOF THE PRESENT DISCLOSURE

An example of the flow of a communication method according to anembodiment of the present disclosure will be described below withreference to FIGS. 20 and 21.

FIG. 20 is a flowchart illustrating a communication method for a firstcommunication apparatus having multiple antennas according to anembodiment of the present disclosure.

As shown in FIG. 20, in step 2000, based on channel states of channelsbetween the multiple antennas of the first communication apparatus and asecond communication apparatus, channel characteristics of a firstchannel from the first communication apparatus to the secondcommunication apparatus in the angle domain are determined.

In step 2010, based on the determined channel characteristics of thefirst channel in the angle domain, a first set of pilot signals aredetermined for being used in the angle domain, the pilot signals in thefirst set of pilot signals being orthogonal to each other.

In step 2020, the first set of pilot signals are transformed into asecond set of pilot signals for transmission over the multiple antennasof the first communication apparatus.

It should be noted that the communication method for a firstcommunication apparatus having multiple antennas according to anembodiment of the present disclosure shown in FIG. 20 may be performedby the electronic device for the first communication apparatus havingmultiple antennas shown in FIG. 6, and it can refer to the abovedescription for details, which will not be repeated herein.

FIG. 21 is a flowchart illustrating a communication method for a secondcommunication apparatus according to an embodiment of the presentdisclosure.

As shown in FIG. 21, in step 2100, channel estimation is performed on afirst channel from a first communication apparatus having multipleantennas to the second communication apparatus based on a second set ofpilot signals from the first communication apparatus, wherein the secondset of pilot signals is determined by the first communication apparatusby the following process: based on channel states of channels betweenthe multiple antennas of the first communication apparatus and thesecond communication apparatus, determining channel characteristics of afirst channel from the first communication apparatus to the secondcommunication apparatus in the angle domain; based on the determinedchannel characteristics of the first channel in the angle domain,determining a first set of pilot signals for being used in the angledomain, the pilot signals in the first set of pilot signals beingorthogonal to each other; and transforming the first set of pilotsignals into a second set of pilot signals for transmission over themultiple antennas of the first communication apparatus.

It should be noted that the communication method for the secondcommunication apparatus according to an embodiment of the presentdisclosure shown in FIG. 21 may be performed by the electronic devicefor the second communication apparatus shown in FIG. 7, and it can referto the above description for details, which will not be repeated herein.

6. OTHER EMBODIMENTS OF THE PRESENT DISCLOSURE

Other embodiments of the present disclosure will be described below withreference to FIGS. 9 and 12.

FIG. 9 is a flowchart illustrating an example of a signaling interactionprocedure performed between a UE and a BS according to the embodiment ofthe present disclosure.

As shown in FIG. 9, steps 9001 and 9002 in FIG. 9 are optional steps.

In step 9001, downlink pilot signals may be transmitted from the BS tothe UE.

In step 9002, a downlink channel may be estimated based on the downlinkpilot signals transmitted from the BS to the UE to determine a channelstate of the downlink channel.

In step 9003, based on channel states of channels between a plurality ofantennas of the UE and the BS, channel characteristics of an uplinkchannel from the UE to the BS in the angle domain are determined.

In step 9004, a first set of pilot signals used in the angle domain isdetermined based on the determined channel characteristics of the uplinkchannel in the angle domain, the pilot signals in the first set of pilotsignals being orthogonal to each other.

In step 9005, the first set of pilot signals used in the angle domain istransformed into a second set of pilot signals (e.g., uplink pilotsignals in the antenna domain or wireless physical channel) fortransmission over the multiple antennas of the UE.

In step 9006, the second set of pilot signals (for example, uplink pilotsignals in the antenna domain or wireless physical channel) is sent tothe BS over the multiple antennas of the UE.

In step 9007, channel estimation is performed on the uplink channel fromthe UE to the BS based on the second set of pilot signals (for example,uplink pilot signals in the antenna domain or wireless physical channel)from the UE having multiple antennas.

In step 9008, channel characteristics of the uplink channel at multipleangles corresponding to the pilot signals in the first set of pilotsignals are determined based on a result of channel estimation performedon the uplink channel from the UE to the BS, and then the uplink channelis reconstructed.

It should be noted that the example of the signaling interactionprocedure performed between the UE and the BS shown in FIG. 9 is similarto the example of the signaling interaction procedure performed betweenthe BS and the UE shown in FIG. 8, and thus similar contents will not bedescribed in detail herein.

Another example of the configuration of an angle domain orthogonal pilotsystem according to an embodiment of the present disclosure will bedescribed below with reference to FIG. 12. FIG. 12 is a diagram showinganother example of the configuration of an angle domain orthogonal pilotsystem according to an embodiment of the present disclosure.

As shown in FIG. 12, an angle domain uplink channel characteristicdetermining module may be configured to estimate a set of indexes ofangle domain ports for a BS which have significant channelcharacteristics of the uplink channel in the angle domain; a pilotallocation module may be configured to allocate orthogonal pilot signalsfor each angle domain port based on the set of indexes of angle domainports which have significant channel characteristics of the uplinkchannel in the angle domain, and then the orthogonal pilot signals aresent to the BS via corresponding RF links and antenna ports after FFTtransformation. It should be noted that the angle domain channel shownin FIG. 12 represents an equivalent channel between the angle domainports and the BS.

In addition, the RF links shown in FIG. 12 correspond to the antennaports one by one, but the present disclosure is not limited to thisexample. For example, the present disclosure can also be applied to anexample in which one RF link connects to a plurality of antennas, and inthis case, a plurality of antennas connected by the same RF link can beregarded as one antenna in the example of the present disclosure.

Still another embodiment of the present disclosure will be describedbelow with reference to FIGS. 22 and 23.

FIG. 22 is a block diagram illustrating the configuration of stillanother example of an electronic device according to an embodiment ofthe present disclosure.

The electronic device 2200 for a multi-antenna communication systemaccording to the embodiment of the present disclosure may include, forexample, a processing circuit 2220 and a memory 2210.

The processing circuit 2220 of the electronic device 2200 used for amulti-antenna communication system is configured to provide variousfunctions for the electronic device 2200 for the multi-antennacommunication system. For example, in the embodiment of the presentdisclosure, the processing circuit 2220 of the electronic device 2200for a multi-antenna communication system may include a channel angledetermining unit 2221, a pilot signal selecting unit 2222, and a pilotsignal transforming unit 2223. The channel angle determining unit 2221may be configured to determine a channel angle between a communicationterminal and a BS based on a state of an uplink channel from thecommunication terminal to the BS. The pilot signal selecting unit 2222may be configured to select a part of a plurality of pilot signals forthe channel angle, wherein the BS has multiple antennas, and themultiple pilot signals support channel angles covered by the multipleantennas of the BS. The pilot signal transforming unit 2223 may beconfigured to transform the part of pilot signals into signals fortransmission over the multiple antennas of the BS.

In addition, according to an embodiment of the present disclosure, thepilot signal transforming unit 2223 in the processing circuit 2220 ofthe electronic device 2200 for the multi-antenna wireless communicationsystem may be configured to transform the part of the pilot signals intosignals for transmission over the multiple antennas of the BS based on aFourier transform.

FIG. 23 is a flowchart illustrating a communication method for anelectronic device according to an embodiment of the present disclosure.

As shown in FIG. 23, in step 2300, based on a state of an uplink channelfrom a communication terminal to a BS, a channel angle between thecommunication terminal and the BS is determined.

In step 2310, a part of a plurality of pilot signals may be selected forthe channel angle, wherein the BS has multiple antennas, and theplurality of pilot signals support channel angles covered by themultiple antennas of the BS.

In step 2320, the part of pilot signals may be transformed into signalsfor transmission over the multiple antennas of the BS.

It should be noted that the communication method for the electronicdevice according to an embodiment of the present disclosure shown inFIG. 23 may be performed by the electronic device shown in FIG. 22, itcan refer to the above description for details, which will not berepeated herein.

7. EXAMPLE OF SIMULATION RESULT ACCORDING TO AN EMBODIMENT OF THEPRESENT DISCLOSURE

An example of throughput rate of a cell in a communication systemaccording to an embodiment of the present disclosure will be describedbelow with reference to FIGS. 24 and 25.

Consider a single-cell FDD large-scale antenna system, the BS isequipped with M antennas and serves K single-antenna UEs simultaneously.The type of antennas used by the BS is ULA or UPA. Specific simulationparameters are shown in the following table.

TABLE 1 specific simulation parameters Pilot design scheme Partiallyorthogonal pilot design Precoding algorithm Zero Forcing Algorithm (ZF)the number M of antennas of BS 64 the number of users in the cell  4antenna type ULA/8x8UPA channel parameters {N_(cl), N_(ray)} {6, 20}Angle spread (horizontal 8 degree direction) Angle spread (verticaldirection) 5 degree uplink channel wavelength λ_(UL) 2d downlink channelwavelength λ_(DL) $\frac{10}{9}\lambda_{UL}$

First, as shown in Table 2, a comparison between the pilot overheadrequired in the traditional scheme and that required in the channelestimation in the angle domain of the present disclosure may beconsidered. Where, it is assumed that the size of a coherent resourceblock is B_(c)T_(c)=200 symbols, B_(c) is the coherence bandwidth, andT_(c) is the coherence time. For the partially orthogonal pilot scheme,three sets of different parameters are considered, which are: (1) N=4,Ns=6. (2) N=6, Ns=9. (3) N=12, Ns=18.

TABLE 2 Comparison of downlink channel resource overhead scheme pilotoverhead traditional scheme, τ = 64  32% The scheme of the present   3%disclosure, N = 4, Ns = 6 The scheme of the present 4.5% disclosure, N =6, Ns = 9 The scheme of the present   9% disclosure, N = 12, Ns = 18

It can be seen that the length of the pilot sequence in the conventionalscheme is the number of the antennas of the BS, causing that the pilotoverhead is very large. However, the angle domain channel estimationscheme using a partially orthogonal pilot signal sequence proposed inthe present disclosure can greatly reduce the pilot overhead. Forexample, with N=4, Ns=6, the pilot overhead is only about 10% of thetraditional scheme.

Further, considering the downlink throughput rate of the cell, if thepilot overhead is r, the downlink throughput rate of the cell iscalculated according to the following equation:

$C = {\left( {1 - r} \right){\sum\limits_{k = 1}^{K}{\log_{2}\left( {1 + {SINR}_{k}} \right)}}}$

-   -   wherein, SINR_(k) is the signal to noise ratio of the kth UE.

FIG. 24 is a simulation diagram of one example of the throughput rate ofa cell in the communication system according to an embodiment of thepresent disclosure. FIG. 25 is a simulation diagram of another exampleof the throughput rate of a cell in the communication system accordingto an embodiment of the present disclosure.

Specifically, FIG. 24 and FIG. 25 show comparison of the downlinkthroughput rate of a cell between the traditional scheme and the schemeof the present disclosure in the case of ULA and UPA antennas,respectively. It can be seen that, compared to the traditional scheme,the angle domain channel estimation method proposed in the presentdisclosure can improve the downlink throughput rate of the cell.Specifically, in the case of high signal-to-noise ratio, the downlinkthroughput rate of the cell is increased by about 26% and 23%,respectively.

In addition, it can note that the angle domain channel estimation methodhas a considerable gain under each SNR condition in the UPA scenario,because the channel sparsity is stronger in the UPA antenna scenario.

8. APPLICATION EXAMPLE

The technique of the present disclosure can be applied to variousproducts.

For example, the UE may be implemented as a mobile terminal such as asmart phone, a tablet personal computer (PC), a notebook PC, a portablegame terminal, a portable/dongle type mobile router, and a digitalcamera, or an on-board terminal such as a car navigation device. The UEmay also be implemented as a terminal performing machine-to-machine(M2M) communication, also referred to as a machine type communication(MTC) terminal. In addition, the UE may be a wireless communicationmodule installed on each of the aforementioned terminals, such as anintegrated circuit module including a single wafer.

For example, the BS may be implemented as any type of evolved Node B(eNB), such as a macro eNB and a small eNB. A small eNB may be an eNBthat covers cells smaller than the macro cells, such as a pico eNB, amicro eNB, or a home (femto) eNB. Alternatively, the BS may beimplemented as any other type of BS, such as a NodeB and a BaseTransceiver Station (BTS). The BS may comprise: a main unit that isconfigured to control wireless communication, also referred to as a BSdevice, and one or more remote wireless headends (RRHs) that are locatedin different locations from the main unit. In addition, various types ofterminals described below may operate as a BS by temporarily orsemi-permanently performing the functions of a BS.

8-1. Application Example of User Equipment First Application Example

FIG. 26 is a block diagram illustrating an example of a schematicconfiguration of a smart phone 900 to which the technique of the presentdisclosure can be applied. The smart phone 900 includes a processor 901,memory 902, a storage device 903, an external connection interface 904,a camera 906, a sensor 907, a microphone 908, an input device 909, adisplay device 910, a speaker 911, a wireless communication interface912, one or more antenna switches 915, one or more antennas 916, a bus917, a battery 918, and an auxiliary controller 919.

The processor 901 may be, for example, a CPU or a system-on-chip (SoC),and controls functions of an application layer and other layers of thesmart phone 900. The memory 902 includes a RAM and a ROM, and storesdata and programs executed by the processor 901. The storage device 903may comprise a storage medium such as a semiconductor memory and a harddisk. The external connection interface 904 is an interface forconnecting an external device (such as, a memory card and a UniversalSerial Bus (USB) device) to the smart phone 900.

The camera 906 includes an image sensor, such as, a charge coupleddevice (CCD) and a complementary metal oxide semiconductor (CMOS), andgenerates captured images. The sensor 907 may include a set of sensors,such as a measurement sensor, a gyro sensor, a geomagnetic sensor, andan acceleration sensor. The microphone 908 converts sounds input to thesmart phone 900 into audio signals. The input devices 909 comprise, forexample, a touch sensor configured to detect touches on the screen ofthe display device 910, a keypad, a keyboard, buttons, or switches, andreceive operations or information input from a user. The display device910 includes a screen, such as, a liquid crystal display (LCD) and anorganic light emitting diode (OLED) display, and displays output imagesof the smart phone 900. The speaker 911 converts audio signals outputfrom the smart phone 900 into sounds.

The wireless communication interface 912 supports any cellularcommunication schemes, such as LTE and LTE-Advanced, and performswireless communication. The wireless communication interface 912 maygenerally include, for example, a BB processor 913 and an RF circuit914. The BB processor 913 can perform, for example, encoding/decoding,modulation/demodulation, and multiplexing/demultiplexing, and performsvarious types of signal processing for wireless communication.Meanwhile, the RF circuit 914 may include, for example, a mixer, afilter, and an amplifier, and transmit and receive wireless signals viathe antenna 916. The wireless communication interface 912 may be a chipmodule on which the BB processor 913 and the RF circuit 914 areintegrated. As shown in FIG. 21, the wireless communication interface912 may include multiple BB processors 913 and multiple RF circuits 914.Although FIG. 21 shows an example in which the wireless communicationinterface 912 includes multiple BB processors 913 and multiple RFcircuits 914, the wireless communication interface 912 may also includea single BB processor 913 or a single RF circuit 914.

Further, in addition to cellular communication schemes, the wirelesscommunication interface 912 may support other types of wirelesscommunication schemes, such as a short-range wireless communicationscheme, a near-field communication scheme, and a wireless local areanetwork (LAN) scheme. In this case, the wireless communication interface912 may include a BB processor 913 and an RF circuit 914 for eachwireless communication scheme.

Each of the antenna switches 915 switches, among a plurality of circuitsincluded in the wireless communication interface 912 (for example,circuits for different wireless communication schemes), the connectiondestination of the antenna 916.

Each of the antennas 916 includes a single antenna element or multipleantenna elements, such as multiple antenna elements included in a MIMOantenna, and is used by the wireless communication interface 912 totransmit and receive wireless signals. As shown in FIG. 21, the smartphone 900 may include a plurality of antennas 916. Although FIG. 21shows an example in which the smart phone 900 includes a plurality ofantennas 916, the smart phone 900 may also include a single antenna 916.

In addition, the smart phone 900 may include an antenna 916 for eachwireless communication scheme. In this case, the antenna switch 915 maybe omitted from the configuration of the smart phone 900.

The bus 917 connects the processor 901, the memory 902, the storagedevice 903, the external connection interface 904, the camera 906, thesensors 907, the microphone 908, the input devices 909, the displaydevice 910, the speaker 911, the wireless communication interface 912,and the auxiliary controller 919 to each other. The battery 918 suppliespower to each block of the smart phone 900 shown in FIG. 21 via feedlines, which are partially shown by dotted lines in the figure. Theauxiliary controller 919 operates minimum necessary functions of thesmart phone 900 in the sleep mode, for example.

In the smart phone 900 shown in FIG. 26, one or more components includedin the processing circuit 720 described with reference to FIG. 7 may beimplemented in the wireless communication interface 912. Alternatively,at least a part of these components may be implemented in the processor901 or the auxiliary controller 919. As an example, the smart phone 900includes a part of the wireless communication interface 912, eg, the BBprocessor 913, or the entirety of the wireless communication interface912, and/or a module including the processor 901 and/or the auxiliarycontroller 919, and one or more components may be implemented in thismodule. In this case, the module may store a program that allows aprocessor to function as one or more components, in other words, aprogram for allowing the processor to perform operations of the one ormore components, and may execute the program. As another example, aprogram for allowing a processor to function as one or more componentsmay be installed in the smart phone 900, and the wireless communicationinterface 912 (eg, the BB processor 913), the processor 901, and/or theauxiliary controller 919 can execute this program. As described above,as a device including one or more components, a smart phone 900 or amodule may be provided, and a program for allowing a processor tofunction as one or more components may be provided. In addition, areadable medium having the program recorded therein may be provided.

Second Application Example

FIG. 27 is a block diagram illustrating an example of a schematicconfiguration of a car navigation device 920 to which the technique ofthe present disclosure can be applied. The car navigation device 920includes a processor 921, a memory 922, a global positioning system(GPS) module 924, a sensor 925, a data interface 926, a content player927, a storage medium interface 928, an input device 929, a displaydevice 930, a speaker 931, and a wireless communication interface 933,one or more antenna switches 936, one or more antennas 937, and abattery 938.

The processor 921 may be, for example, a CPU or a SoC, and controls thenavigation function and other functions of the car navigation device920. The memory 922 includes a RAM and a ROM, and stores data andprograms executed by the processor 921.

The GPS module 924 uses GPS signals received from GPS satellites tomeasure the position of the car navigation device 920, such as latitude,longitude and altitude thereof. The sensor 925 may include a set ofsensors such as a gyro sensor, a geomagnetic sensor, and an air pressuresensor. The data interface 926 is connected to, for example, anon-vehicle network 941 via a terminal (not shown), and acquires data,such as, vehicle speed data, generated by the vehicle.

The content player 927 reproduces contents stored in a storage medium,such as a CD and a DVD, which is inserted into the storage mediuminterface 928. The input device 929 include, for example, a touch sensorconfigured to detect touches on the screen of the display device 930,buttons or switches, and receive operations or information input from auser. The display device 930 includes a screen such as an LCD or an OLEDdisplay, and displays images of the navigation function or reproducedcontents. The speaker 931 outputs sounds of the navigation function orreproduced contents.

The wireless communication interface 933 supports any cellularcommunication schemes, such as LTE and LTE-Advanced, and performswireless communication. The wireless communication interface 933 maygenerally include, for example, a BB processor 934 and a RF circuit 935.The BB processor 934 may perform, for example, encoding/decoding,modulation/demodulation, and multiplexing/demultiplexing, and performsvarious types of signal processing for wireless communication.Meanwhile, the RF circuit 934 may include, for example, a mixer, afilter, and an amplifier, and transmit and receive wireless signals viathe antennas 937. The wireless communication interface 933 may be a chipmodule on which the BB processor 934 and the RF circuit 935 areintegrated. As shown in FIG. 22, the wireless communication interface933 may include multiple BB processors 934 and multiple RF circuits 935.Although FIG. 22 shows an example in which the wireless communicationinterface 933 includes multiple of BB processors 934 and multiple RFcircuits 935, the wireless communication interface 933 may include asingle BB processor 934 or a single RF circuit 935.

Further, in addition to cellular communication schemes, the wirelesscommunication interface 933 may support other types of wirelesscommunication schemes, such as a short-range wireless communicationscheme, a near-field communication scheme, and a wireless LAN scheme. Inthis case, the wireless communication interface 933 may include a BBprocessor 934 and an RF circuit 935 for each wireless communicationscheme.

Each of the antenna switches 936 switches, among a plurality of circuitsincluded in the wireless communication interface 933, for example,circuits for different wireless communication schemes, connectiondestination of the antennas 937.

Each of the antennas 937 includes a single antenna element or multipleantenna elements, such as multiple antenna elements included in a MIMOantenna, and is used by the wireless communication interface 933 totransmit and receive wireless signals. As shown in FIG. 22, the carnavigation device 920 may include a plurality of antennas 937. AlthoughFIG. 22 shows an example in which the car navigation device 920 includesa plurality of antennas 937, the car navigation device 920 may alsoinclude a single antenna 937.

In addition, the car navigation device 920 may include an antenna 937for each wireless communication scheme. In this case, the antennaswitches 936 may be omitted from the configuration of the car navigationdevice 920.

The battery 938 supplies power to each block of the car navigationdevice 920 shown in FIG. 22 via feeder lines, which are partially shownas dotted lines in the figure. The battery 938 accumulates powerprovided from the vehicle.

In the car navigation device 920 shown in FIG. 27, one or morecomponents included in the processing circuit 720 described withreference to FIG. 7 may be implemented in the wireless communicationinterface 933. Alternatively, at least a part of these components may beimplemented in the processor 921. As an example, the car navigationdevice 920 includes a part of the wireless communication interface 933,eg. the BB processor 934, or the entirety of the wireless communicationinterface 933, and/or a module including the processor 921, and one ormore components may be implemented in the module. In this case, themodule may store a program that allows a processor to function as one ormore components, in other words, a program for allowing the processor toperform operations of one or more components, and may execute theprogram. As another example, a program for allowing the processor tofunction as one or more components may be installed in the carnavigation device 920, and the wireless communication interface 933, eg,the BB processor 934, and/or the processor 921 may execute the program.As described above, as a device including one or more components, thecar navigation device 920 or a module may be provided, and a program forallowing the processor to function as one or more components may beprovided. In addition, a readable medium having the program recordedtherein may be provided.

The technique of this disclosure may also be implemented as an on-boardsystem (or vehicle) 940 that includes one or more blocks of the carnavigation device 920, the on-board network 941, and the vehicle module942. The vehicle module 942 generates vehicle data, such as vehiclespeed, engine speed, and failure information, and outputs the generateddata to the on-vehicle network 941.

8-2. Application Example of Base Station First Application Example

FIG. 28 is a block diagram illustrating a first example of the schematicconfiguration of a BS to which the technique of the present disclosuremay be applied. Wherein, the base station is shown as eNB 800. Wherein,the eNB 800 includes one or more antennas 810 and a base station (BS)device 820. The BS device 820 is connected to each antenna 810 via RFcables.

Each of the antennas 810 includes a single antenna element or multipleantenna elements, such as a plurality of antenna elements included in aMultiple Input Multiple Output (MIMO) antenna, and is used by the BSdevice 820 to transmit and receive wireless signals. As shown in FIG.23, the eNB 800 may include multiple antennas 810. For example, themultiple antennas 810 may be compatible with multiple frequency bandsused by the eNB 800. Although FIG. 23 shows an example in which the eNB800 includes multiple antennas 810, the eNB 800 may also include asingle antenna 810.

The BS device 820 includes a controller 821, a memory 822, a networkinterface 823, and a wireless communication interface 825.

The controller 821 may be, for example, a CPU or a DSP, and operatesvarious functions of the BS device 820 in a higher level. For example,the controller 821 generates data packets based on data in signalsprocessed by the wireless communication interface 825, and delivers thegenerated packets via the network interface 823. The controller 821 canbundle data from multiple baseband processors to generate bundledpackets and deliver the generated bundled packets. The controller 821may have logic functions that perform controls such as radio resourcecontrol, radio bearer control, mobility management, admission controland scheduling. This control can be performed in conjunction with nearbyeNBs or core network nodes. The memory 822 includes a RAM and a ROM andstores programs executed by the controller 821 and various types ofcontrol data, such as a terminal list, transmission power data, andscheduling data.

The network interface 823 is a communication interface for connectingthe BS device 820 to a core network 824. The controller 821 maycommunicate with the core network node or another eNB via the networkinterface 823. In this case, eNB 800 and core network nodes or othereNBs may be connected to each other through logical interfaces, such asS1 interfaces and X2 interfaces. The network interface 823 may also be awired communication interface or a wireless communication interface fora wireless backhaul line. If the network interface 823 is a wirelesscommunication interface, the network interface 823 can use a higherfrequency band for wireless communication than the frequency band usedby the wireless communication interface 825.

The wireless communication interface 825 supports any cellularcommunication schemes, such as Long Term Evolution (LTE) andLTE-Advanced, and provides wireless connection to terminals located in acell of the eNB 800 via the antennas 810. The wireless communicationinterface 825 may generally include, for example, a baseband (BB)processor 826 and an RF circuit 827. The BB processor 826 may perform,for example, encoding/decoding, modulation/demodulation, andmultiplexing/demultiplexing, and performs various types of signalprocessing in layers such as L1, Medium Access Control (MAC), Radio LinkControl (RLC), and Packet Data Convergence Protocol (PDCP). Instead ofthe controller 821, the BB processor 826 may have some or all of theabove-described logic functions. The BB processor 826 may be a memorythat stores a communication control program, or a module that includes aprocessor and related circuits that are configured to execute a program.An update program may change the functions of the BB processor 826. Thismodule may be a card or blade inserted into a slot of the BS device 820.Alternatively, the module may also be a chip mounted on a card or blade.Meanwhile, the RF circuit 827 may include, for example, a mixer, afilter and an amplifier, and transmit and receive wireless signals viathe antenna 810.

As shown in FIG. 28, the wireless communication interface 825 mayinclude multiple BB processors 826. For example, the multiple BBprocessors 826 may be compatible with multiple frequency bands used byeNB 800. As shown in FIG. 28, the wireless communication interface 825may include multiple RF circuits 827. For example, the multiple RFcircuits 827 may be compatible with multiple antenna elements. AlthoughFIG. 23 shows an example in which the wireless communication interface825 includes multiple BB processors 826 and multiple RF circuits 827,the wireless communication interface 825 may also include a single BBprocessor 826 or a single RF circuit 827.

In the eNB 800 shown in FIG. 28, one or more components included in theprocessing circuit 620 described with reference to FIG. 6 may beimplemented in the wireless communication interface 825. Alternatively,at least a part of these components may be implemented in the controller821. For example, the eNB 800 includes a part of the wirelesscommunication interface 825, e.g., the BB processor 826, or the entiretyof the wireless communication interface 825, and/or a module includingthe controller 821, and one or more components may be implemented in themodule. In this case, the module may store a program for allowing theprocessor to function as one or more components, in other words, aprogram for allowing the processor to perform operations of one or morecomponents, and may execute the program. As another example, a programfor allowing the processor to function as one or more components may beinstalled in the eNB 800, and the wireless communication interface 825,eg, the BB processor 826, and/or the controller 821 may perform theprogram. As described above, as a device including one or morecomponents, the eNB 800, the BS device 820, or a module may be provided,and a program for allowing the processor to function as one or morecomponents may be provided. In addition, a readable medium having theprogram recorded therein may be provided.

Second Application Example

FIG. 29 is a block diagram illustrating a second example of theschematic configuration of a BS to which the technique of the presentdisclosure may be applied. Wherein, the base station is shown as eNB830. The eNB 830 includes one or more antennas 840, a BS device 850 anda RRH 860. The RRH 860 is connected to each antenna 840 via RF cables.The BS device 850 and the RRH 860 may be connected to each other via ahigh-speed line such as a fiber optic cable.

Each of the antennas 840 includes a single antenna element or multipleantenna elements, such as a plurality of antenna elements included in aMultiple Input Multiple Output (MIMO) antenna, and is used by the RRH860 to transmit and receive wireless signals. As shown in FIG. 24, theeNB 830 may include multiple antennas 840. For example, the multipleantennas 840 may be compatible with multiple frequency bands used by theeNB 830. Although FIG. 24 shows an example in which the eNB 830 includesmultiple antennas 840, the eNB 830 may also include a single antenna840.

The BS device 850 includes a controller 851, a memory 852, a networkinterface 853, a wireless communication interface 855 and a connectioninterface 857. The controller 851, the memory 852, and the networkinterface 853 are the same as the controller 821, the memory 822, andthe network interface 823 described with reference to FIG. 23.

The wireless communication interface 855 supports any cellularcommunication schemes, such as Long Term Evolution (LTE) andLTE-Advanced, and provides wireless communication to a terminal locatedin a sector corresponding to the RRH 860 via the RRH 860 and the antenna840. The wireless communication interface 855 may generally include, forexample, a BB processor 856. Except that the BB processor 856 isconnected to the RF circuit 864 of the RRH 860 via the connectioninterface 857, the BB processor 856 is the same as the BB processor 826described with reference to FIG. 23. As shown in FIG. 24, the wirelesscommunication interface 855 may include multiple BB processors 856. Forexample, the multiple BB processors 856 may be compatible with multiplefrequency bands used by eNB 830. Although FIG. 24 shows an example inwhich the wireless communication interface 855 includes multiple BBprocessors 856, the wireless communication interface 825 may alsoinclude a single BB processor 856.

The connection interface 857 is an interface for connecting the BSdevice 850 (the wireless communication interface 855) to the RRH 860.The connection interface 857 may also be a communication module forcommunicating the BS device 850 (the wireless communication interface855) to the above described high-speed line of the RRH 860.

The RRH 860 includes a connection interface 861 and a wirelesscommunication interface 863.

The connection interface 861 is an interface for connecting the RRH 860(the wireless communication interface 863) to the BS device 850. Theconnection interface 861 may also be a communication module forcommunication on the above high speed line.

The wireless communication interface 863 transmits and receives wirelesssignals via the antenna 840. The wireless communication interface 863may generally include, for example, an RF circuit 864. The RF circuit864 may include, for example, a mixer, a filter and an amplifier, andtransmit and receive wireless signals via the antenna 840. As shown inFIG. 24, the wireless communication interface 863 may include multipleRF circuits 864. For example, the multiple RF circuits 864 may supportmultiple antenna elements. Although FIG. 24 shows an example in whichthe wireless communication interface 863 includes multiple RF circuits864, the wireless communication interface 863 may also include a singleRF circuit 864.

In the eNB 800 shown in FIG. 29, one or more components included in theprocessing circuit 620 described with reference to FIG. 6 may beimplemented in the wireless communication interface 825. Alternatively,at least a portion of these components may be implemented in thecontroller 821. For example, the eNB 800 includes a part of the wirelesscommunication interface 825, e.g., the BB processor 826, or the entiretyof the wireless communication interface 825, and/or a module includingthe controller 821, and one or more components may be implemented in themodule. In this case, the module may store a program for allowing theprocessor to function as one or more components (in other words, aprogram for allowing the processor to perform operations of one or morecomponents), and may execute the program. As another example, a programfor allowing the processor to function as one or more components may beinstalled in the eNB 800, and the wireless communication interface 825(eg, the BB processor 826) and/or the controller 821 may perform theprogram. As described above, as a device including one or morecomponents, the eNB 800, the BS device 820, or a module may be provided,and a program for allowing the processor to function as one or morecomponents may be provided. In addition, a readable medium having theprogram recorded therein may be provided.

6. CONCLUSION

According to some embodiments of the present disclosure, overhead ofchannel estimation may be reduced.

According to some embodiments of the present disclosure, it is alsopossible to further increase the data throughput rate of thecommunication system while maintaining lower overhead of channelestimation.

An example has been described in which the communication system is asystem complying with LTE or LTE-A, but the embodiments of the presentdisclosure are not limited to the related example. For example, thecommunication system may be a system that complies with anothercommunication standard. In this case, the UE may be another terminaldevice and the base station may be another base station.

In the description of this specification, reference throughout thisspecification to “embodiment” or similar expressions means that aparticular feature, structure, or characteristic described in connectionwith the embodiment is included in at least one embodiment of thepresent invention. Therefore, the appearances of terms “in theembodiments of the present disclosure” and similar expressions do notnecessarily refer to the same embodiments in this specification.

Those skilled in the art will appreciate that the present disclosure isimplemented as a system, apparatus, method, or computer readable mediumas a computer program product. Accordingly, the present disclosure maybe embodied in various forms, such as a complete hardware embodiment, acomplete software embodiment (including firmware, resident software,microprogram code, etc.), or may also be implemented as animplementation of software and hardware, which will be referred to as“circuit,” “module,” or “system” below. In addition, the presentdisclosure may also be embodied in any form of tangible media such as acomputer program product having computer-usable program code storedthereon.

The related description of the present disclosure will be described withreference to flowcharts and/or block diagrams of systems, apparatuses,methods, and computer program products according to specific embodimentsof the present disclosure. It will be understood that each block in eachflowchart and/or block diagram, and any combination of blocks in theflowcharts and/or block diagrams, can be implemented using computerprogram instructions. These computer program instructions may beexecuted by a machine consisting of a general-purpose or special-purposecomputer processor or other programmable data processing device, and theinstructions are processed by a computer or other programmable dataprocessing device to implement functions or operations described in theflowcharts and/or block diagrams.

Flowcharts and block diagrams of architectures, functions, andoperations that may be implemented by systems, apparatuses, methods, andcomputer program products according to various embodiments of thepresent disclosure are shown in the drawings. Thus, each block in theflowcharts or block diagrams may represent a module, section, or portionof program code that includes one or more executable instructions toperform a specified logical function. It should also be noted that insome other embodiments, the functionality described in the blocks maynot be performed in the order shown in the drawings. For example, thetwo blocks that are connected in a figure blocks may in fact be executedsimultaneously or, in some cases, may be performed in the reverse orderdepending on the function involved. In addition, it should be noted thatblocks in each block diagram and/or flowchart, and combinations ofblocks in the block diagram and/or flowchart, may be implemented by adedicated hardware-based system or by a combination of dedicatedhardware and computer instructions, to perform a specific function oroperation.

What is claimed is:
 1. An electronic device for a base stationcomprising multiple antennas, comprising: a memory for storing computerinstructions; and a processing circuit configured to execute the storedcomputer instructions to: based on channel states of channels betweenthe multiple antennas of the base station and a user equipment (UE),determine channel characteristics of an uplink channel from the basestation to the UE in an angle domain; based on the determined channelcharacteristics of the uplink channel in the angle domain, determine asecond set of pilot signals for estimating channel characteristics of adownlink channel from the UE to the base station in the angle domain,wherein the second set of pilot signals is used in a spatial domain; andcontrol the multiple antennas of the base station to transmit the secondset of pilot signals to the UE.
 2. The electronic device according toclaim 1, wherein the processing circuit is further configured to executethe stored computer instructions to: based on the determined channelcharacteristics of the first channel in the angle domain, determine afirst set of pilot signals used in the angle domain, the pilot signalsin the first set of pilot signals being orthogonal to each other; andtransform the first set of pilot signals into the second set of pilotsignals.
 3. The electronic device according to claim 1, wherein thechannel states of the channels between the multiple antennas of the basestation and the UE correspond to channel states of channels from the UEto the multiple antennas of the base station, and the processing circuitis further configured to execute the stored computer instructions to:based on the channel states of the channels from the UE to the multipleantennas of the base station, determine channel characteristics of thedownlink channel from the UE to the base station in the angle domain,and determine the channel characteristics of the uplink channel in theangle domain based on the channel characteristics of the downlinkchannel in the angle domain.
 4. The electronic device according to claim1, wherein the channel states of the channels between the multipleantennas of the base station and the UE correspond to channel states ofchannels from the multiple antennas of the base station to the UE, andthe processing circuit is further configured to execute the storedcomputer instructions to: determine the channel characteristics of theuplink channel in the angle domain according to the channel states ofthe channels from the multiple antennas of the base station to the UE.5. The electronic device according to claim 1, wherein the processingcircuit is further configured to execute the stored computerinstructions to: transform the channel states of the channels betweenthe multiple antennas of the base station and the UE to obtain channelcharacteristics of a corresponding channel in the angle domain.
 6. Theelectronic device according to claim 5, wherein the processing circuitis further configured to execute the stored computer instructions to:based on the channel characteristics of the corresponding channel in theangle domain, select N angles from the angle domain at which the channelcharacteristics are significant, where N is a natural number greaterthan or equal to 1, the number of pilot signals in a first set of pilotsignals is greater than or equal to N, and the first set of pilotsignals are used for the N angles, respectively.
 7. The electronicdevice according to claim 1, wherein the base station communicates witha plurality of UEs, and the processing circuit is further configured toexecute the stored computer instructions to: determine a first set ofpilot signals used in the angle domain for the plurality of UEs, whereinrespective pilot signals in the first set of pilot signals areorthonormal to each other with respect to angles as a union of the Nangles having significant channel characteristics of the correspondinguplink channel from the base station to each of the multiple UEs in theangle domain, wherein N is a natural number greater than or equal to 1.8. The electronic device according to claim 1, wherein the base stationcommunicates with a plurality of UEs, and the processing circuit isfurther configured to execute the stored computer instructions to:determine a first set of pilot signals used in the angle domain for theplurality of UEs, wherein in the case where the number of pilot signalsin the first set of pilot signals is minimum, respective pilot signalsin the first set of pilot signals are orthonormal to each other withrespect to angles corresponding to N angles having significant channelcharacteristics in a corresponding uplink channel from the base stationto one of the plurality of UEs in the angle domain, wherein N is anatural number greater than or equal to
 1. 9. An electronic device for auser equipment (UE), comprising: a memory for storing computerinstructions; and a processing circuit configured to execute the storedcomputer instructions to: perform channel estimation of a downlinkchannel from a base station comprising multiple antennas to the UE basedon a second set of pilot signals from the base station, wherein thesecond set of pilot signals is determined by the base station by: basedon channel states of channels between the multiple antennas of the basestation and the UE, determining channel characteristics of an uplinkchannel from the base station to the UE in an angle domain; based on thedetermined channel characteristics of the uplink channel in the angledomain, determining the second set of pilot signals for estimatingchannel characteristics of the downlink channel from the UE to the basestation in the angle domain, wherein the second set of pilot signalsused in a spatial domain.
 10. The electronic device according to claim9, wherein the processing circuit is further configured to execute thestored computer instructions to: based on a result of the channelestimation, determine channel characteristics of the downlink channel atmultiple angles corresponding to the second set of pilot signals, whichare fed back to the base station.
 11. The electronic device according toclaim 9, wherein the processing circuit is further configured to executethe stored computer instructions to: before performing channelestimation on the downlink channel, send an uplink reference signalsused for estimating a channel state of the uplink channel from the UE tothe base station.
 12. The electronic device according to claim 10,wherein the processing circuit is further configured to execute thestored computer instructions to: feed back significant channelcharacteristics among channel characteristics of the downlink channel atmultiple angles and indexes of the pilot signals.